This took me 5 years to realise...
Mario accidentally caused Axol's death...
You may think I'm wrong, but once I explain, it'll make a lot of sense:
It dates back in 2020, in SMG4: Mario gets WOKE. When Mario sees a weird Roblox noob button, he pressed it on Axol, thinking it would be something stupid, but it turns out, it took Axol to the internet graveyard. When Mario is then sent there by SMG3, Axol is no longer the same, being trapped there for 5 years (actually a few weeks, but you get the idea), and his inkweaver ended up breaking, so he could no longer anime to life. His clothes were now rugged, and he had a scar on his right eye. When he got out, he either used a different pen for drawing anime, or used his broken inkweaver as a sword. A year later in SMG4: If Mario was in... Anime, Axol gave Mario a quest to find his missing half of inkweaver, which turned out to be used as a door stopper by SMG3 in the internet graveyard. Axol was happy to have his pen working again, and drew his first creation ever since his pen was broken, and him and Mario celebrated. However, this was short-lived in the next episode, SMG4: The day he arrived, when Shrek clones started appearing at Peach's castle and SMG4 thought Axol was behind it, thinking Shrek was an anime (debatle), but he was actually writing a love book about Melony. This led to the events of Zero, Axol being possessed, the universe almost ending, *Sniffs*, Melony sacrificing Axol to save the world.
Mario didnt kill Axol out of malice, it was pure stupidity that indirectly caused Axol's death.