What parts do you want to be similar? Dying Light 2 has a large open world, parkour, and an interesting story and lots of side things to do. Plus its combat is melee plus bow, very similar to Assassin's Creed. Off the top of my head, I can't think of a more similar game, unless you were talking about other points of similarity, like historical settings and what have you. It's in first person, if that makes a difference to you.
The first how ever many Yakuza games had open worlds and melee combat in third person, but no parkour.
Dishonored might be similar. I've never played it. Maybe someone who has can chime in on that one, but from what little I know about it, it seems like it might be close.
Assassin's Creed: Odyssey was pretty much an action RPG in an open world. There are a LOT of games like that, so knowing what parts of Assassin's Creed you liked would be a big help. Off the top of my head...
Horizon: Zero Dawn: has a lot more ranged combat than AC games but it's fairly similar.
Witcher (especially Witcher 3): there isn't so much sneaking, but the stories in the quests are VASTY better!
Rocksteady's Batman Arkham games (especially Arkham City): combat is quite a bit different than AC, but it sure seems more fun to me.
Mad Max: vehicle combat as well as hand to hand
Middle Earth: Shadow of Mordor/War
The later Tomb Raider games: less sneaking, more shooting
Saints Row: The Third: less sneaking, more crazy
Yakuza 0: less sneaking and more crazy again, but also some serious thrown in