The manga has the now common premise of the main character reincarnating in another world as a monster after dying. OK, so he becomes a slime monster. That's all fine and dandy, and it's all done quite well. The biggest problem is the OP skill he gains right off the bat with the Great Sage mode. Basically throughout the story he faces many "challenges" but generally speaking has a quite easy time dealing with them since he's pretty much the most powerful one around right off the bat. It's frankly much more fun to watch actual struggles instead of "minor struggle? ---> activate super cheat skill ---> struggle over". It doesn't necessarily make the series bad, but all the encounters could've been much more compelling and had a "sense of danger" in them if the balance of power between the MC and the rest of the world wasn't so out of whack.