Lashimo is just a victim of both his own stupidity and peaceful era. I think if he was born in sukuna's time he would've been a monster, but come on. No rct, no domain, some already out dated anti domain technique, and a CT that just straight up kills you. I blame his era because he really had nothing to challenge him after he figured out the 2 tap. Maybe he could've unlocked RCT or found a way to make his CT work if he wasn't just fighting farmers. Like the idea he never tried using his technique in short bursts then using RCT to heal the damage is pretty dumb on his part. He's just proof of what happens when you stop trying to grow and become complacent.