Omega alloy is undisputedly the strongest alloy in all of the bossfights multiverse
The Tyrant's gold is very tough amd was meant for battle
Reinforced Resisteel is Resisteel (a strong alloy) mixed with cosmic steel.
Cosmic still is made from a limitless scale, galatic gold, solar sapphire, and universal iron
The stick and egg alloys are strong as to reasons I do not know