Pantheon, Tahm Kench, or Urgot?

You need to think about what you want to do in a game.

is an early game murderer who can brutalize his enemy during the lane phase, snow ball other lanes with ease, and see the game closed out extremely fast. However, if you fail to do this, you become dead weight.

is a bruiser's bruiser. He becomes a tough and murderous late game power house who can soak up tons of punishment and effectively murder.. just about anything. However he's not distinctly strong during the early or even mid game.

is a tank. He's good at all phases, but as the game goes on you become less and less directly influential. What I mean by that is you transition to being the one carrying - by killing enemies directly - to being in a more supportive role with your positioning, ally saves, CC, and tankiness.

is a tank who functions similar to Tahm, but with a more brutal early game and a less noteworthy late game. Sion's bug was recently fixed which returned him to a 51% winrate; he's no longer something to write home about. However he does, when mastered, have a positively brutal early game which transitions into a tremendous mid game.

The problem is that he drops off like a rock at about 25 minutes.

Once you hit that point you become nothing more than a wall of meat which brings some CC, and your biggest strength is actually your ability to engage with a combination of righteous glory and R.

Pantheon is as strong as an empowered baron cannon minion. Urgot is two whole waves. Tahm Kench is the baron himself and you should feel bad if you play him because he's broken op nerf pls

If you want to learn Panth watch Keegun. Keegun is the rank 1 Panth or either climbed to Rank 1 with Panth something like that. Either way the guy is super good with him.

If you want to learn Sion just watch Tilterella. He's basically the guy who popularized a lot of the current Sion play styles.

Tahm idk who plays him a lot so can't help you there.

Tahm is funny as hell and hard to kill Pantheon is just snowbally, but with a bad lategame Urgot is a juggernaut with insanely high damage but takes time to learn since you can't freeze waves at all.

I'd recommend tahm, if I were you