Best late game champions for each role?

Late game huh?

TOP - I mean, really. Are you surprised?

JUNGLE - Sejuani may have a weak early game but if you can get her to a full build AP bruiser she's scary.

MID - The little master of Evil becomes a nightmare late game. He turns enemy AP against them and infinitely scales!

ADC - her mobility late might be a bit of a problem but that AoE damage is insane!

SUPPORT - If you can build some AP on Soraka her heals are nigh unstoppable!

Honestly...this team scares me. It might not have the tankiest champions but Soraka heals makes up for it in spades and there is so much peel with Sej + Veigar Huge AoE Stun + Darius...being Darius that Soraka can be protected to heal. Damn...this team gets scarier the more I think about it.

Top-Nasus Jung- Nasus Mid- Veigar Adc- Depends on the team compositions, most think it's between Vayne, Kog'maw, and Cait Support- Veigar

Edit: Tristana too

There are 4 infinite scaling champs in the game. Probably them. Top: Nasus Jungle: Sion Mid: Veigar Support: Thresh

Kindred can also be considered too but Kindred isn't infinite scaling. Kindred I think caps out at 20 marks collected which is a direct 30% hp removal per auto attack. You can kill a tank in just 4-5 auto attacks with this steroid alone. Other mentions are Cassiopeia, Vayne, Kog'maw, Viktor, Master Yi, Azir, and Vladimir.

Top: Moa - Incredibly tanky while still doing a lot of damage. Has lots of CC and some mobility. Overall everything you'd want from a top laner. (For those who keep saying Nasus, remember he's easily kited. He has a strong late-mid, early-late game. But does start to fall off late game.)

Mid: Viegar - Scales hard. But the real reason is that large AoE stun that can change a teamfight. Both together make him a monster.

Jungle: Varies heavily. Must have a strong range presence, even if not ranged.

Support: Naut. With the rest of the team having enough damage, this guy can go all CC. And he has a lot of it. Thresh is amazing too, but has less impact overall in a teamfight than Naut. While Naut has less catch potential. But not much less.

ADC: Varies Pick comp - Vayne - Self peel galore without giving up much damage. Has no AoE presence though. Teamfight comp with low dive - Jinx - Lots of AoE. Teamfight comp with high dive - Kog'Maw - Use that range. Destroy everything. General - Sivir - Strong team utility, good AoE, spellshield. While not really a hyper carry, she's very strong late game.

TThere isn't really a best late game champion, team comps matter more than individual picks. Even a weaker late game pick could have tremendous late game impact if they make a critical pick on a champion (i.e. Leona who falls off late game finds an opening with her long range ult) But if you're talking about single champions excluding the infinite scalers...

Top: Poppy

Mid: There are far too many different playstyles... Xerath for long range/poke, Azir for control mage, etc. etc. Assassins fall off hard though

ADC: Tristana, safest, huge range, huge as steroid, huge snowball with jump

Support: This varies far too much since the impact of a support fluctuates so drastically. Blitz could single handedly end a game with a pull, Janna could perfectly ruin an engage and tornado critical gap closers for her hypercarry, Sona could land a 5 man ult, Bard ult as well, who knows?

Jungle: Well, there are many roles too. I think Sejuani is worth mentioning though, since her long range, long lasting initiation is one of a kind, but still, too many variables.