F-Rank Necromancer from the Start, Fusing with the Grim Reaper

The world undergoes a global mutation, disaster descends, and monsters run rampant. To resist the monsters, the world becomes digitized. At eighteen, everyone gains a combat or support class through awakening and class advancement, then levels up and grows stronger by killing monsters. Gu Qing awakens an F-rank combat class, the Bleach mage, from the start, and is mocked as a useless, fragile weakling who can summon only two skeleton soldiers. But Gu Qing activates the Infinite Class Compendium. As long as his class proficiency reaches its maximum, he can unlock new classes, and classes can even fuse. [Bleach Mage] + [God-Tier Chef] = Hidden Class [Bleach Lord] [Beast Tamer] + [Goddess's Apostle] = Unique Class [Spirit God Sovereign] [Shadow Dominator] + [Blood Emperor] + [Bleach Lord] = Mythic Class [Bleach] Not long afterward, when the Evil God invades, Gu Qing faces it alone, waving his hand to summon an army of a million undead, goddesses of every race surrounding him, and shattering the Evil God with a single slash. You say an F-rank Bleach mage is weak. What does that have to do with my A-rank magic swordsman, S-rank alchemy god, SSS-rank Spirit God Sovereign, and mythic-rank Bleach...?