I'm about to get back into ranked again and and since I haven't really played since last season I was curious who the most common bans are currently

Singed,tryndamere,mordekaiser,kennen,riven,gangpla nk,lee sin, dr mundo

Adding on to him ^ , Shen , Rammus

Lee Sin and Singed are always always always banned

Tryndamere, Shaco, Shen are almost always banned

Morgana, Shyvana, Rumble, Kennen, Olaf, Riven are all very viable in threes, and you might consider banning if you have trouble with them.

Singed and Trynd are permaban.

Shaco regularlly banned. Syvana/Yorick/Kennen worth a ban.

I don't really know for sure, many are viable, not many are OP. It kinda depends on your teams playstyle. many common bans include: shen, WW, trynd, shaco, shyvana, renek, morde, singed, voli, jax, wukong, olaf, riven, lee sin, mundo. It varies greatly in my own opinion.

Anything that begins with SH
Then Mundo
Then Lee sin
If you have got this far down then ban Janna

singed/tryn/shaco/lee are the only champs i can say are banned every time, at least in the level I'm currently at.

other 2 bans differ, but i like to ban yorick

I frequently ban Twisted Fate and Ryze. Both are very strong mid lanes who pubstomp pretty hard.