What you say makes sense from the trope perspective, but I don't think it's the case for the Sentry. And I blame the writers for hiding important information in Sentry character bios.
Sentry didn't struggle or go crazy from too much power. He struggled due to the responsibility he had. That's pointed out in the Sentry character bio in the second Sentry series. It's stated that flying across the planet non-stop and saving various people was wearing him down. That's too much responsibility for anyone to handle. He is almost the only hero on Marvel Earth who has that kind of power and versatility. Imagine Spider-Man talking about power and responsibility. But Spider-Man can't stop a mugging at the end of the city because he doesn't have the power set. Sentry can stop a mugging on the other side of the planet. This is why he had CLOC, a robot servant, monitor crime and disasters and tell Sentry what to prioritize. In a fight against Sentry Iron Man hacks CLOC and Sentry receives all of the information at once – and breaks down because he can't make the call about who gets to live and who doesn't.
What I just wrote is in itself an amazing concept and something that should have been explored in Sentry comics. Sentry is someone with a lower set of morals. He's gonna rip you apart if you endanger others and there is no one on Earth who can stop him. You can do a lot of things with that. But that has been covered in a character bio and a few panels in various comics. It's just... missed opportunities left and right with this character and Marvel.
And I wouldn't even say that the super soldier serum elevated Sentrys mental illness. That's not only not necessary, but is also... less depressing than the alternative: His mind remained the way it is but his body changed to a point where drugs, toxins and ultimately also important medicine simply doesn't work on him. So now you have this mentally ill guy who is powerful to a point where nothing can harm him, but nothing can improve his mental state either. And schizophrenia is not a mental illness you can just let free roam. You need medications for it to keep it in check. It's a very, very complex illness and with the powers of a reality warper, you could do some really crazy stuff with it. But all Marvel does is manifest it in the form of the Void, over and over and over and over and over again. The character has been in comics for 23 years by now, on and off, and every single time we see him it has to do something with the Void.
If you ask me, then Sentry stories write themselves. I'm fairly confident I could write 100 Sentry comics without ever devolving into the Void themes for more than 3-4 panels. I do think that Void is an incredibly important and appealing part of the Sentry, but not when it's all there is. Sentry already has his own Rogues gallery which can be expanded on, he has potentially interesting supporting characters, has more than enough themes and personality surrounding him to easily carry everything on his own etc. But no, Marvel keeps going back to the Void and even worse, immediately killing the Sentry off. For an supposedly immortal character he has been more dead and a zombie than he has been alive. It's like a running gag at this point.
What happened to that? Did Cates move on to another company and creator-owned characters? Haven't been following comics in a while now.
And knowing how Marvel comics like to tie themselves to the MCU, I wouldn't be surprised if we saw stuff on the Sentry as soon as the Thunderbolts trailers and we see the Sentry. But boy, am I concerned about that movie. The Sentry casting is... eeeh. (If the rumors are true.)