Thread:Mattardis/@comment-30408599-20180429204545/@comment-30408599-20180503190638

I don't think Bowser actually has a way to counter Shendu's immortality. I should point out though, Bowser can also turn Shendu into something harmless, a brick even, but I checked out S1 Ep13, and he doesn't have much problem being turned into something useless.

Bowser might win if he uses the Vibe Scepter (<can control emotions), or the Minimizer (<can shrink the opponent), but he only ever used these once each, and he might not even have them anymore. Based on your research, Bowser's best chance would be to turn Shendu into a rock/brick.

https://legendsoflocalization.com/super-mario-bros/manuals/#game-story