It really annoys me too. Do you have any recommendations of mangas with strong-willed MCs?
Saving 80,000 Gold Coins in the Different World for My Old Age - No op powers, just being able to travel between worlds. Uses modern tech and her wits to take no shit from others.
Potion Tanomi de Ikinobimasu! - Same author as above. Not physically strong, still an op power, but mostly uses words, manipulating others and quick thinking to get out of things she doesn't want to do. Even to the point of hurting herself (not permanently but still) at one point.
Arafoo Shachiku no Golem Master - MC is willing to concede up to a reasonable point, but at the end of ch5 and in ch6 he decides enough is enough and basically threatens the noble trying to take advantage of him with war if the noble continues.
Isekai de Skill wo Kaitai shitara Cheat na Yome ga Zoushoku Shimashita: Gainen Kousa no Structure - MC is OP as hell because of one single thing he can do. And he knows it. Gives me slight one punch man vibes the way battles go. :P
Versatile mage and Rebirth of the urban immortal Cultivator - Chinese wuxia web toons, but still pretty good. And they both really take no shit from anyone. :P
Kujibiki Tokushou Musou Harem-ken - Actually just does what he wants to do so far, rather than following what others tell him to do.
Isekai de Skill wo Kaitai shitara Cheat na Yome ga Zoushoku Shimashita: Gainen Kousa no Structure
the dude is steadily becoming the type to get lead around and doesnt stick with any rebellious attitude
Konjiki no Word Master...
is a better example
Arifureta shokugyou de sekai saikyou
gets badass and doesnt give a shit
Solo Leveling
badass to the max
Dungeon Seeker
definitely badass
Hero? I Quit That a Long Time Ago
badass and hilarious
Class ga isekai shoukan sareta naka ore dake nokotta n desu ga
super ultra badass
Kuro no Shoukanshi
only listens to his goddess wifeu and everyone else can suck it
Saikyou Mahoushi no Inton Keikaku
strongest mage of all, just wants a break and cannot be culled by anyone
The Reincarnation Magician of the Inferior Eyes
still pretty new but so far he seems to fulfill your preferences
Maou-sama Retry
Badass OP awesomeness
Player Reborn
so far so good
Maou Gakuin no Futekigousha
about as OP as it gets
Most of these MCs are so weak-willed. In the latest chapter they're basically deciding on who can have him like he's some kind of property to pass around. And he just goes along with them as if he doesn't have any choice in the matter, even though he's probably powerful enough to take on a small army by himself. Same for so many other isekai stories. Luckily there are a few MCs that don't take shit like that from others, but I wish there were more of them...