Countering Trundle?

Gnar is ranged, and can poke him out without getting poked back. He also has Hop for getting out of and around his pillar. Malphite. He stacks armor, and Trundle is an AD bruiser. Maokai. He builds AP, and Trundle's Q can't steal that. Dr. Mundo. Outsustains and doesn't rely on AD stacking to poke. Cho'gath. Similar sustain, similar poke. If you are having trouble against him with Urgot, then you should change how you play against Trundle. Against lane bully bruiser types, Urgot is meant to use his Q for zoning, his W to kite, and his E to go in once it's time to all-in.

Trundle is a tank-killer. If you go full tank he can't kill you but later in the game he will just ult you and steal all your HP and resistances. It's probably better to go damage dealers vs him so that you can beat him out during the laning phase.

It's not all about counterpicks either. With Trundle you have to fight him outside of his windows of power.

You don't want him to lifesteal off of you with his frozen ground ability, so try to bait it out then disengage and avoid fighting until it wears off.

Also you can try to front-load your damage. Burst him before he bites you so that you still have your AD to scale with, then wait out the debuff and go in for another trade when you have your AD back again.

I recommend buying bramblevest or executioner's calling. He relies on his passive, his frozen ground ability, and his ultimate to heal up. If you can reduce this you will significantly reduce his effectiveness in trades.

Specifically regarding his passive, he's going to passively heal a lot just from minions dying around him, so it's important to trade often once you have either of these items, so that he cannot get the free healing from it.

Poppy? Smash him into his wall

I like playing trundle because it kinda feels like he has no glaring weaknesses but he also doesnt dominate anyone. You can build to fit the lane in most cases and with his ult he can teamfight. gnar is a tough lane but im only gold so idk if this opinion is valid if youre higher elo

Play champions that are mobile and don't rely on building defense and for the love of god don't rush armor. If you get an early kill on him you can snowball on him pretty easily. He can't be completely shut down due to how his kit works, but if you're looking to make his life hell pick a ranged AP champion with short CDs and easy mana management. There is nothing he can do to you unless you let him.