1st it was almost boring SAO Alicization but if you haven't checked it out Alicization War of the Underworld little slow at first then at around episode 4 or 5 it just goes dark in the violence than SAO is known for. Now the other one is really dark and that's ReZERO -Starting Life in Another World- Season 2. It seems normal for a few episodes then it starts to get twisted and dark and I last watched episode 11 and I realized the person that scripted this had a really twisted and brilliant mind. The episodes are like the last episode of future diary when you find you closest friends are just fucked up and will kill you on a whim out of self interest. Highly recommend ReZERO second season if action and having the unexpected worse thing happen that could happen keeping you questioning everything not droned out is your thing then this will do it.