What are the best toplaners when behind?

No champ is good at being behind. Thats basically being good at losing.

Some champs need to win early, while other champs need to simply survive till late game, but no champ is good at being behind, because if you are behind with a strong early champ, you would just be farther behind with a strong late game champ

Irelia can recover well, Maokai isn't useless in teamfights, Nasus can farm forever, Singed can proxy forever, and Mundo just builds tank anyway.

mundo mundo mundo mundo and veigar

It might sound crazy, but Nasus is one of the best recovery champion because of his unqiue skills.

So in a game Vi (JG) kept ganking our fed Bot and Ok-ish Mid while ignoring Top Temmo despite the fact Temmo had one kill from Pre-Buff fight and that just threw the balance. Despite getting useless ganks before Vi stopped trying, I pushed Outer and Inner turrets with 0/5/1 and 50 stacks.

Point 1 - Nasus is powerful at split-pushing even when behind, if ignored

Later in game, I farmed enough CS gold for enough CDR and soon I was spamming Q and racking up 300 stacks.

Point 2 - Nasus can recover from having no stacks, also can farm with E effectively. To farm off Nasus is a danger with his ult, to ignore Nasus to allow stacks. I was ignored and this was a fatal mistake that allowed me to recover in just minutes of free-farming

I got my 400 stacks, I got my items, I go mid and I tanked all the fights despite lacking gold... Also bursted with my Q.

Point 3 - Even behind, Nasus is a effective tank and his Q will sustain him quite nicely.

Irelia: I've seen her come back when everyone was 14 and she was level 1 because of d/c. She ended up winning us the game.

Akali: when played well and the enemy team are dumb can come back.

Vlad: He gets a power spike at 9 and you can go defensive to turtle in lane.

Cho'gath: Silence and pop up can be a game changer

Yorcik: Play safe if you're doing bad and in team fights put your ult on who ever is fed. Like a Master YI