Lucifers brains won't do a difference in this battle.
Think about it, how would the remains of a 50 pounds brain or a 10 pounds brain scattered all over the floor make a greater difference?
Not much the Beyonder can do the Lucy. Lucy's Durability is of the charts when he's ready for it. He can fashion any energy the Classic Beyonder throws at him into anything he wants it to be. Such is his power.
Beyonder was causing massive damage by thinking too much. By being angry, he was tearing apart the Multiverse. He embodies a Multiverse quintillions of times larger than the infinite Marvel Multiverse in size and power, and he created it. He beat a planet of Celestials in H2H. He had the Living Tribunal trembling. Beyonder wins.
He never fought the LT. The LT has never since shaken. Abstracts quaking in fear? OMG. He made a universe quintillions times bigger larger than the marvel multiverse? would you say it's bigger than the marvel omniverse that Is putty in the LT's hands?
Beyonder "classic is one of a kind" and not even LT can beat him, Luc wouldnt have the power to stop the classic one, but he does have ultimate manipulation tho.
Beyonder just takes it if he doesnt hasitate or else he could be manipulated by Luc and even lose his power to him.
Rolf he never had to fought the LT he made him piss his pants in fear. He even made someone stronger then LT cry. He WAS that multiverse he dident make that.
lucifer wud take this, powerless on wit alone. he has infinite will and it manifests in many many ways. not to forget people, he DID outsmart and defeat yahweh, a being stronger than classic beyonder. lucifer himself is compareable easily, he rules his own multiverse and has created teh original one and he can do it again and again, not ot menion that neither the void nor the demiurgic multiverse shattering explosion even scathed him at ground zero. he is effectively beyond multiversal level. the near megaversal death has no hold over him, nor does destiny anymore. when he finally escaped later in the void, the entire enormity of another creation forming with himself/yahweh/micheal and its due course was seen/comprehended and taken in by him in the blink of an eye. he wud be the godhead in primum mobile with all of yahweh's might if he had chosen to be but he didnt like the idea. he was so unique and powerful infact that yahweh himself admitted that he had done what even yahweh cud not, and wanted to amalgamate with him which he straight out refused.
before, having read half of lucifer, id have said beyonder wins. but any1 who has completely read the entire thing and his appearances in sandman can never say that beyonder has the upper hand here. lucifer wins. no1 beats the devil. not to mention, beyonder is THE most gullible/insecure/misguided character in marvel and hence the easiest for lucifer to use his own power againt himself{which is mostly how the llightbringer works}