Don't wanna be that guy but, Olaf?
Still breaking the game if you can stay at the bottom long enough to build your Olaf with rageblade, IE, or whatever is strong on him right now (or just get lucky). Berserker, in general, is a pretty strong choice alone and it is quite easy to force the comp. People will say "Just do '(insert strategy)' to counter it" but the fact of the matter is I can't change the entirety of my comp just to counter the Olaf as by the time an Olaf will appear my comp will be on the way and adapting will be a risky compromise (let alone will make the game boring if I have to build the same way every game). Teamfight Tactics will only give you what it wants, and to suggest adapting to counter Olaf and berserker every game is simply unreliable. It is not an underestimate, in my experience, to say he is a very common occurrence, and I will see a carry Olaf (normally in the top 2 I may add) in more than 3/4 of games. I could use him and rush the comp but running meta and top picks all the time usually make a game quite stale, and I would be disappointed to see such a fun game lose what made it such a reliable alternative to League as a result of the same problems that make League frustrating.
ready for the downvotes btw, Rant over. Thank you :)