Both are apparently immune to normal weaponry, however Aku has been damaged although by a stupidly powerful weapon yet has higher end feats, while Void has much lower feats yet hasn't been injured.
The feats in question are:
Aku- ignored the attacks of various middle age armies and reflected their arrows/weapons back on them without any effort, and also ignored the attacks of a race that had been living for a unknown period of time at the bottom of the sea [massive pressure] in a very weak form [big octopus/squid, he was toying with them].
The only known effect to hurt him is the Sword forged from the purity of a human soul/spirit, wielded by a might warrior [the Sword has been shown to have greater effect as it's wielder grows in skill/prowess] and imbued with the power of the heads of 3 divine pantheosn [Odin, Vishnu, Horus-Re], and that affects him as a normal sword might although in the hands of a sufficiently powerful wielder it also burns whatever it touches, but he can regenerate the body mass disintegrated by the sword even when sliced in half and left with a amount of body mass the size of a frog.
Void (as far as I Know) has the feat that when the Skull knight stabbed him (Without Void noticig him) the Knight's sword was reflected back at him.
[Any experts on the series might be able to add info here].
My question is who would be judged more powerful?
After all, by board policy it would probably be Aku who has a known limit, yet Aku was injured by something far more powerful than any sword seen in Berserk and has feats far in excess of Void, so should we judge by the lower known limit or the far higher limit?
If anyone want's to argue this as a simple rumble/vs rather than as the bit of board ruling/policy/me wanting to learn about how no-limit's fallacies, it is meant to by, then here are a few scenarios for ya
:A) Aku vs Void, taking the assumption that they can over-ride each other's reality warping. [in a straight up fight].
B) All of Aku's minions [including Demongo, Mad Jack, limitless robot armies] agaisnt the forces held by the Apostles and the currently living Apostles known.
C) Who has shown greater intelligence/cunning/planning etc..., Aku or the God hand in general?
D) Who appears to be more dangerous, the idea of evil/god [master of the god hand], or Aku's original form that fought 3 skyfathers at the same time and might have won.