When Alex was supposedly hurt, many tried to heal him but failed. At first, he thought the wounds were just too advanced but after experiencing Vendetta's upgrade ability, he finally realized why something this amazing happened.
After combining the two secret combined techniques, his body which is no longer that of an ordinary human body was simply trying to adapt to the power. Vendetta's upgrade power did not heal him, instead, it just accelerated the process.
With the adaptation process completed, Alex realized his blood had turned golden and his power level has risen to the SS ratings! The fusion of the two secret techniques was incomplete yet they were enough to raise his power to that level.
But it is still incomplete!