>>280423647
>No matter how much effort one puts in, every living being has an intrinsic limit to its growth. Too much power becomes unbearable and overwhelms its host, turning it into a mindless, rampaging monster. To ensure that we do not enter the realm where we lose all purpose and reason, God has set limits to the growth of every being. The mechanism with which growth is controlled is called the limiter. ”
— Dr. I. Genus[1]

So having power past the limit of humanity makes people into mindless monsters according to this explanation. We know Saitama's case had him pushing to near death (because he's naturally so weak) with an unbreakable determination. It seems that human willpower and a drive and dedication can allow one to keep pushing farther without succumbing to becoming a monster, yet those who become unhealthily obsessed are more sucsceptible to such madness. Garou seemed to be straddling the line, both shapeshifting into a sort of monster costume as well as pushing his growth farther. When he called Saitama unfair, this is the point where he's subconsciously decided what he's striving for is impossible to achieve through his own strength. It's the point where he's lost confidence in himself and where his determination falters. And like Darkshine, when his confidence was lost he got weaker. That's how I see it anyway. His monstrous form looks like paper mache as Saitama punches through it, it's a big hollow doll. It looks intimidating but it's all for show. I mean, he's still tremendously powerful, but not as much as when his determination burned bright.