Ever wondered what it would look like if your 14 year old self would have written a story about one guy being OP and saving the world in secret? Then give your inner 14 year old child a treat with this. It is such an entertaining, over the top and well executed show. Don't expect a heavy story, don't expect demon-slayer level of animation, or deep character writing. But see it as a perfect power-trip with a ton of comedy, and a psychopath who never misses, no matter how much he ass-pulls his ideas and explanations.
Take One-Punch-Man, make him a psychopath that doesn't want to get found out in his day-to-day form, and let him play edgy dark guy which never misses. Then add a plain but working story on top and round it up with really good fights, and a good potion of comedy. Now you set this up in a world of magic (and something about isekai, doesn't matter actually). This is TenSura if Rimuru just wanted to look cool.
Also yeah some ecchi shit no one asked for, what ever.
