Mr Devourer, Please Act Like a Final Boss is a Manga/Manhwa/Manhua in english language, Action series, english chapters have been translated and you can read them here. You are reading chapters on www.mgeko.cc fastest updating comic site. The Summary is

[By the studio that brought you Solo Leveling with Redice studio!]
The era of dungeon raids has finally arrived. The Seven Great Evil Dungeons— the seven strongest dungeons that are considered impossible to conquer. Deep within the most infamous dungeon, Primordial Core, lives the worst boss monster of all time, the “Devourer.” “Does it make any sense that the dungeon boss was dozing off until the humans were right in front of him?!?!” Because of the constant visits from humans, the doorsteps of the Primordial Core never dry up, and the nagging the Devourer hears never stops…?! “Ha… I don’t want to do this.”