Play who you really like, I have seen people say a ton of champs are OP, like riven, nunu, lulu, zed, lb, shaco, azyr, annie, ez, nid, ekko, morg, lux, wukong, yoric, alistar, malz, skarner, hecarim, eve, mundo, galio, fizz, karma, syndra(mobile burst &CC), kassadin, ryze, kennen, maokai, yi, TF, varus, vlad, zillian, zyra, xin
Other champions are known to be strong like braum, akali, ahri, brand, cho'gath, darius(maybe), fiddle(CC), old taric(rework doesn't feel to good, so if its new taric, you can try but I wouldn't recomend), GP, janna, rengar, nasus, olaf, rammus, tahm, voli, singed, velkoz
If you know how to use a champion, they can be overly strong, honestly I don't know why people are like "X Y Z champs make the game unfun" because there is more viability for URF then normal SR.