Well, to be honest, I wouldn't change a thing about this game. It just seems like one could probably argue that every hero in the game performs AT LEAST two actions (As the first two on their own can move both ways horizontally or vertically).
My complaints about following the theme is something more technical, and honestly maybe should even be acknowledged considering this is the first time I've actually taken the time to participate in a jam in any meaningful way, so my judgement might be made off of naivety and lack of experience with what is generally accepted as "Following the Theme"
My though about this lead me to giving it a three out of five as far as keeping to the theme, because, in my opinion, the theme of "Only One" seemed to feel more like "Only Two" in this game... But, I've enjoyed the design so much that I gave 5/5 in the other two categories.
While I understand that you wanted to keep to the theme very strongly, if I weren't the only one that pointed this out, I wouldn't pay any attention to it if I were you. It's always great to win a jam, but I personally think you have something more here.