Everything? Weird glitchy hitboxes, slashing several times at an enemy and having the weapon go through the model but no damage taken (shortsword is terrible for this), agility/i-frames as a stat, the weird 'sliding on ice' when getting staggered by a hit, hitting enemies but not "feeling it" - two handing a mace on the knights in Heides tower, it feels like the weapon goes straight through the model and only the (often delayed) sound effect and the numbers on screen tell you it hit. Eternal spinning on the spot enemy AI (looks even more ridiculous when it's a huge boss like Jabba the Hut), that same delayed third or fourth hit to a combo that so many of the enemies have. Poise being useless apparently. Wear a shit ton of armour and still get chain staggered by a tiny dagger. Rolling and jumping just feels off and unreliable. The cardinal sin of attacking in different directions when locking on (if I wanted free aim I wouldn't lock on) - it's difficult not to be holding a direction in a game like this. Not stacking button commands during rolls etc (worked great in DS1, why change it?
And that's just PvE, I gave up on PvP a long time ago when I realised SM destroys not only low-level pvp, co-op and counter-troll builds but also any level pvp and co-op because soul level is now completely meaningless. Plus rubberband rollback p2p connections worse than anything I've seen in the previous two games. I get a lot of people like being SL400 and being able to equip anything and everything with only one character - that's not me, and if I'm in a niche of Souls players, I'm in a niche, but something tells me the niche isn't that all that small. I hear the exact same criticisms when listening to ENB and A German Spy's videos amongst others.
As Booshka said, there's still some great stuff in the game, I love making a new character and landing at the farfire and buying the cat ring and blasting through the Gutter to get down to the fragrent branch of yore down there to unlock the Shaded Woods asap, stuff like that. I love how you explore at low level in all the Souls games.