If you play Sejuani or Rammus, this is why you should ban Trundle every single game

Basically when Sejuani has her passive up or Rammus casts his W and Trundle ults them he subtracts armor from them based on that buffed amount, this effect is even more severe if aftershock is also in effect. The problem with this is that when those effects wear off, Trundle is still subtracting the amount he stole from them while they were under those massive buffs. They literally have negative resistances for the rest of Trundle's ult duration. If you've ever seen one of those two champions surprisingly get instantly blown up while Trundle is on the other team, this is why.

This silly interaction probably results in the hardest counters in the game and it seems really shitty for people who play these two champions to be completely shut down by getting counterpicked by a champion that can flex to three different roles.