Valhalla has easily the worst combat of the three full on RPG AC games. Long attack animations every other time you finish an enemy off whilst all the others stand there patiently, for example.

Then there's the unbelievably terrible barred doors that are absolutely everywhere (they are in mirage as well) which is the shittest, lowest effort puzzle they could have ever thought of and they repeated it every fifteen feet. Good luck maintaining stealth whilst you have to go back outside and circle the building looking for a hole in the wall to shoot an arrow through in a completely plausible and not at all deliriously stupid way.

Then there's the offensively shallow side missions, the barely having anything to do with assassins for the vast majority of the shockingly bloated game, the sheer bugginess (tall grass used to disappear when I got close to it, all the way through the game), spending twenty minutes finding a chest that you spotted with your bird only to discover it's impossible to access until you're on or have completed a specific story mission. Having to wait for your raiders to open bloody chests, despite them being buggy idiots who will stand around ignoring you for five seconds before moving towards it as slowly as possible - all this, including three horrendous barred doors, in the middle of a Viking raid, because a Viking is incapable of breaking open a door somehow. Awful.

I love assassin's creed, I've played all of them. Valhalla ruined the RPGs.