Slight spoiler warning if you havent seen the entire thing.
Towards the end of the anime and manga (current adaptation as of october 2021) he gains 4 ultimate skills namely Gluttonous king Beelzebub (evolved version of predetor/glunttony after fusing with/sacrificing the merciless unique skill), Lord of wisdom raphael (evolved state of great sage after fusing with/sacrificng degenerate unique skill), Lord of vows Uriel (made by raphael using unlimited imprisonment as a base after releasing veldora from stomach) and finally Lord of storms Veldora (made by analyzing veldoras remains)
On top of that his evolution to a demon lord granted him several other skills and abilities as well as improving on his already existing ones. as for the light and web novels, im not too sure bc i havent read them, but hes basically a god in one of them, not sure which.
He’s a god in the web novel and most likely will be one in the light novel as he is already the most powerful character in it
In the volumes not yet officially translated Rimuru combines his ultimate skills and gains the ultimate abilities:
Ciel
Shub niggurath
Azathoth (this ultimate skill has nihility collapse (LN) / turn null (WN) which I honestly didn't quite understand as it said that it is immensely destructive energy produced through a separate dimension (called chaotic nuclear dimension in vsbattle).
The separate dimension was actually imaginary space (also called the chaos world) which is literally the stomach of rimuru which is an infinite space where the energy of nihility collapse / turn null creates and is stored so that later ciel converts it into magicules.
He was only one true ultimate superpower and that was Raphael. That skill started out as a super computer whos only goal was to complete the goal of her user and evolved in the ultimate skill Raphael. But if you think on that question wouldn't Raphael be the real MC but only hidden? She maybe a skill but she would also be a Goddess for there is no question she cannot answer 🤯
What do you think?