I refer to him as he, cause he was originally male in his former world, anyway rimuru has a serious case of cis, his subordinates like diablo and shio have all sorts of disgusting hax, and rimuru is stronger than them yet in character he doesn't use any reality warping nonsense like his subordinates, he uses some sealing and soul manipulation, while his subordinates have existence erasure, fate manipulation, reality warping, causality manipulation etc.
See the cis? He can gain any of his subordinates abilities and every time they evolve they can gain any of his skills, you would think he would spam his subordinates abilities, nope, rarely ever uses them, albeit he hasn't needed to so far.
Assuming the cis is off, rimuru has some ridiculous abilities like reality warping via turning reality into illusions, turning illusions into reality, fate manipulation, existence erasure, causality manipulation, mid godly regen, attacks which can transcend space-time, probability manipulation etc etc.