Well I've been playing 'duels of champions' lately, a trading card game based on the 'heroes of might & magic' universe. Mechanically it's pretty awesome: like a mix of 'magic the gathering' and mojang's new 'scrolls' and it involves hero units.
It was my first TCG and I was really digging it, until I ranked up enough to get matched with serious opponents and I started to suspect some balance problems... So out of morbid curiousity I entered a few small tournaments. My theory being that if certain decks, cards or heroes show up unnaturally often in tournaments, they're probably overpowered.
Lo and behold: out of about 30 opponents I faced only two were not playing either a necropolis or an inferno deck. In case you're wondering: necropolis decks are basically black decks from magic the gathering and ditto for inferno decks and red decks.
Furthermore, with the exception of some newbies, all their decks were filled to the rim with the exact cards I suspected to be overpowered. And finally, 14 out of 17 necropolis decks I faced were using the "whatshisface, lord of pestilence" hero.
I haven't played since.
So yeah, that would be my entry: whatshisface, lord of pestilence from duels of champions.