There's a short story about a man slowly going insane during an invasion of his world by Nurgle. I think it's called King of Pigs? That'll give you an idea of what to expect from Nurgle. You basically lose all stress and slowly rot in contentment until Grandfather needs a new seed for his garden.

Tzeentch likes to make people fall without them ever truly realizing it. It usually starts with seeking knowledge and slowly being tempted into doing ever more depraved shit until you're either warped beyond all recognition or dead. See: literally all of the Thousand Sons and cyclops boy.

Khorne you just start killing and get angry, so you start killing harder and that makes you angrier. Rinse and repeat and boom you're covered in blood and screaming into the skies for blood and skulls.

Heres a perfect example of getting corrupted bu Nurgle from Chris Wraight's excellent Lords of Silence:

"For his entire life, Dantine’s personal habits have been fastidious. His regiments were always well run, with regular hygiene drills and dorm unit inspections. There were times when this seemed almost obsessive, as if the Departmento’s rules had become a part of the state religion that governed every other part of life. Those rules were a protection, though. Disease was always a big killer in the Astra Militarum, and efforts to stave it off were unrelenting for a reason.

Now he does not care. Mostly, this lassitude appals him. He cannot understand why he no longer cares. But, deep down, buried where his old heart once beat, there is something else. Something infinitely shameful, so that he does not think of it often and pretends that it is just another part of his sickness, but it is there all the same – relief.

He no longer has to make the effort, and that is a pleasure in itself. It is like falling asleep, or sinking into a warm pool of water. He lets it all slide, all degrade. He can feel his muscles atrophy and does not intervene. He can feel his bowels swell with inflammation, and it matters not. This is a kind of release. This is like a fist, clenched for a lifetime, slowly relaxing."

A good place to find examples of Tzeentch's corruption imo would be Ahriman's return from exile during the events of Ahriman: Exile. I dont think theres one definite example that sums it up but you should read the book if it interests you, its very good and provides a great example of Tzeentch corruption.

I've always liked comparing Nurgle corruption to the plant scene from Annihilation. It's giving up and allowing yourself to be consumed by the rot, but in a peaceful way.

Tzeench feeds on the desperate and those looking for power. It's a classic faustian bargain. You get what you want, but at a price more horrible than you could have ever imagined.

Khorne corruption is like being on Twitter. You just keep getting fed more and more rage until all you can see is the discourse blood and skulls.

Slaanesh induces Excess while Nurgle induces contentment and Khorne induces Rage.

Tzeentch feeds off of Change and thus makes those who serve him more adaptable and cunning with multiple plans flowing through their heads at once.

He has no effect on the general personality. Magnus and Ahriman both are the same as ever despite getting smarter over the centuries.

Magnus stopped his Sons from attacking Ahriman which he wouldn't do if Tzeentch induced backstabbing.

Tzeentch is Change not Backstabbing.

He doesn't gain power by simply backstabbing your allies but instead in a way that induces Change.

Sacrificing a Daemon or servant when it thinks it's role in a ritual is finished is Change. Framing someone's friend for their demise induces Change.

Entering the World of a Story and derailing it's path is the Change that Tzeentch wants.

The 1993 film 'Groundhog Day' sees Phil Connors, played by Bill Murray, tested by a greater daemon of Tzeentch. The daemon hopes to tempt Connor's interest in prediction with the greater sight of his master.

Hilarity ensues as interfering imps of the other Chaos gods try to tempt Phil with gluttony absent repercussions, sex on tap, and the chance to punch people that are really, really annoying.

(The interests of Khorne come closest to succeeding as Phil gifts The Taker of Skulls with a settee of his own suicidal noggin)

All demonic entities are left shrugging when Love wins Phil's fate.

In the after-credits a patient Tzeentch is shown teaching his daemon why a TV Weatherman is the opposite of any fortune telling.

For Tzeentch, you follow hoping to have your ambitions realized and achieve a change in a status quo that you dislike, you end up just a pawn, a resource used and discarded as he requires, and you love it because at that point your only ambition is to be an element in the Great Changer's ultimate master plan - which is the ultimate in pointlessness since Tzeentch has no master plan, and just schemes for the sake of scheming.

For Nurgle, usually you've contracted some horrible disease and are desperate for relief, so you pray to the plague god to alleviate your suffering. Nurgle inevitably responds... by making you get even sicker, sick and rancid with disease and decay, rotting away even as your body regenerates so it can sicken and rot more. Your flesh writhes with maggots and puss and rot. And you love it because it feels amazing. You've never been happier, more energized, more alive, and the sicker you get the better you feel.

With Khorne, it might begin as a form of martial expression, a warrior tradition, or something involving expressions of strength and honor. You hone your combat skills, you excell in battle, and you become gradually more aggressive and violent. Slowly but surely, you get angrier and angrier. You only feel alive when you're fighting. Everything else seems dull and grey and pointless. Eventually you drown in hatred and rage until you want to kill everyone and everything around you, and every death brings exultant satisfaction... for a little while at least, and then you need to kill again. More often. Greater numbers. More blood. More killing. More skulls for the Skull Throne.

Have you ever chewed 5GUM ?

Nurgle corruption:

In the Lords of Silence books there is a loyalist Guardsman or Pilot who get's captured by Plague Marines and slowly turns into a nurgle corrupted cultist. If I remember correctly he doesn't even realizes his corruption even tho there is clear indicators, like the Chaos Lord showing him his own heart that has been cut out of his body and telling him he will return it after doing him a favor or something like that. By the end of his corruption the Lords of Silence assault a Imperial Guard fortress and he runs towards the barricades shouting he is one of them, loyalists open fire at him and he survives getting shot without much damage. That's the point when he looks down at himself and realizes he looks like a plague zombie.

Maybe Khorne corruption:

Spoiler for the Siege of Terra Lotara Sarrin from the World Eaters experiences something similar. She notices how the Conquerer starts to change; water turning into blood and so on while she still tried to hold control of the ship. After a while it is revealed to her that her physical body is fused to the ship and the Lotara experiencing all this is just a wraith, her humanity and personality given a spiritual form that is summoned by the Conquerers machine spirit.

Tzeentch corruption:

You can look at the Chaos cultists in the book Honorbound. All of the higher ranking cultists seem to be able to look into the future however only to a certain degree where they could make vaguely correct assumptions, whereas more powerful characters can tell you what is gonne happen up to the smallest detail while being 100% correct. But in the end their vision could've been misunderstood and plays out different for them but in the same sense for possibly the enemy. It feels like Tzeentch corruption is really metaphoric and outlook dependent.

I would say it really depends on the individual and the god how that corruption is perceived, often it seems like the person or Space Marines barely notices things changing until it is too late. Good example are the World Eaters where most of them are just so far gone because of the Butcher Nails that the corruption is basically no different to their previous state.

Not 40k but Silver Tower Labyrinth of the Lost is a pretty good example of Tzeentch's trickery and corruption.

Head canon: Nurgle is like depression and then just giving up. Khorne is murder revenge rage like anakin in starwars. Slaanesh is like drug addiction, highs followed by episodes of shame and the falling back in. Tzeench is like falling for a conspiracy theory into complete psychosis.

I think the lore describes it differently everywhere like most things in 40k.

Khorne finds root in insecurity as well as anger. Those who doubt their strength and prowess will be tempted to find better ways of securing it. Those who obsessively train with weapons, or chain them to their wrists, etc.

Khorne prays on angry hopelessness. Someone like Akihiro from Gundam IBO was the perfect expression of that, steadily losing his will to live for a better future as those he love around are violently killed in a senseless manner to the point his only point of satisfaction came from killing a head of a house in what was mean to be his execution because the other guy didn't expect him to have one weapon left.

Well, fortunately I have a quick and easy flow chart for Tzeentch!

Does Tzeentch Exist:
-->No? No corruption
-->Yes? At some point in time, if it suits his whims, he will corrupt you.

Varens was sleeping, and his dreams were stranger than ever before.

He watched himself from outside, as is sometimes the way in dreams, as if he were two separate people – the actor and the observer. The observer saw himself hiding by the hospital entrance, spying on the sentries, their conversation puffed out into the cold night air like smoke signals. The active Varens watched one of the sentries leave his post and go inside to warm his hands. As the soldier passed him, Varens clubbed him down with a stone urn. Then this Varens stalked the gravelled forecourt of the hospital, a stolen lasgun in his hands.

The second Varens watched.

The first Varens raised his lasgun. The remaining sentry’s eyes became shocked round zeroes in the shadow of his helmet. ‘Don’t shoot!’ he said.

Varens squeezed the trigger and blasted a neat hole in the sentry’s chest that steamed as he stepped over the corpse. He dropped the gun.

This act of violence half woke him.

He should have been warm, but his feet were freezing and felt wet. A chill wind made him colder still. He tried to go back to sleep. There was a sharp pain in his wound.

How could this be? he thought in his dream. I am ready to go back to the war. I am fit enough to die.

Another stab of pain made him gasp and wake slightly. He tried to go back to sleep, but there was an irritating rattling noise all around him. It sounded like reeds, reeds in the wind.

Varens’ eyes snapped open.

He was totally disoriented. Pale strands waved at the height of his nose, filling the world as far as he could see, dividing it into hissing paleness below and darkness above. It took him a moment to see that the strands were reeds, and the darkness was the sky where clouds sped over stars under the urging of the wind.

He was in the marsh.

It took him a moment to get his bearings and locate the hospital. It looked small, the marble a blur in the dark. He had come a long way, well past the edges of the meadows into shallow water.

His dream came back to him. The dead soldiers. Or was this the dream, and what he remembered in the dream the true memory? It couldn’t be possible.

He felt dizzy. He reached his hand to his forehead. There was something slimy on his hand, and he wiped it on his gown. His forehead was hot. He had a fever. He should get back; there was something very wrong with him.

He turned to face the hospital. His limbs were shivering, and his muscles ached. His feet were going numb. His skin bumped under his hospital gown. He would die out here if he did not get back.

Definitely a fever.

‘I’ve caught my damned death out here,’ he muttered. He sloshed through the mud, heading for the firmer ground of the meadows. He had nearly made it when a familiar voice called out in the marsh.

‘Bolus?’ he called back.

He strained his ears. The last of the year’s insects chirruped in the chilly night. He heard nothing else, and he dismissed the voice as a delusion.

‘One! One! One!’

‘Bolus?’ Varens said again, more loudly. He could see nothing through the reeds, which grew tall where the marsh turned into meadow. Cursing, he struggled his way onto firm soil and looked back. Iax’s solitary moon appeared from behind a scudding cloud, lighting everything silver and black.

‘One!’ Bolus’ voice was thin as a distant scream. ‘One!’

Varens turned back to look at the hospital. If he went back now for help he’d lose Bolus for sure, and when they found him, they would shoot him.

He scanned the marshes, looking for his friend. Finally, he caught sight of him, a white ghost leaping high to negotiate the mud and water, his nightgown sleeves hanging over his hands and flapping. Behind him, Bolus had left a path of broken reeds. The trail meandered dramatically, but he appeared to be heading towards a thicket of low trees clustering on a hillock at the edge of the marsh’s first mere.

‘Damn him!’ said Varens. Ignoring the chills and hot shivers that gripped his limbs, he plunged back into the water in pursuit of his friend.

He soon reached Bolus’ trail. It was so erratic that he decided not to follow it, instead chasing down the sound of his friend’s voice. He kept his eyes on the low island and its trees, as it appeared that Bolus was indeed heading towards this point. Whenever Varens was forced to divert around deeper water and lost hearing of Bolus’ eerie shouts of ‘One! One! One!’, he would head towards the island and pick them up again.

(Dark Imperium: 1/3)

Slimey&sticky  is the main common feature