Board Thread:Show-Related Questions and Answers/@comment-24301813-20160926205826/@comment-61573-20161109103848

He may be resistant to magic, but not apparently physical harm. Cue the ice spikes and well, it's going to hurt! Or just encase him in a block of solid ice.

Plus, strong as Hyde is, I would assume Marshmallow is a lot stronger! Then we have the size and leverage issue, fighting a small giant is about as impractical as it sounds. So if Marshmallow gets involved, Hyde would be tossed around like a rag doll. Also, Marshmallow has ice claws, more physical damage.....

Also, powers that affect water might get around protective magic, since every living thing is mostly water and therefore, freezing it isn't going to do that lifeform much good......