This stupidity of him suddenly losing his power is honestly just piss poor writing.. like, yeah, had to give him something of a challenge.. But a full fucking reset while his comrades are getting tortured/killed? Obviously with the theme of the story they are just gonna be beat up a bit and he comes back with lots of power... but that's just murder on ones suspension of disbelief.
I thought these manga artists had editors that would tell them when they wrote something stupid...