THE LOVE TRIANGLE!
Everyone loves a love triangle!
Oh, and endless power-ups, of course! What's not to love about a character who can never get defeated by anyone and who just becomes EVEN MORE POWERFUL OUT OF NOWHERE the moment a strong enemy appears?
And what about being isekai'ed by truck-kun? Better yet, what about a story in which somebody gets isekai'ed by truck-kun only to end up in a world where there's endless power-ups and a love triangle (or maybe even a harem!) in store for them? 
Oh... wait.