Really fascinating concept, but as everyone's already pointed out, the only consistent strategy is having a ton of defense or HP and just lowering enemy damage. My winning run I never got lucky enough to get shops and just got 50 rests so I tanked all the damage and whittled everyone's Damage down to 0. It was also difficult to understand the negative mechanic at first but once it clicked I really liked it.
It's also kinda sad the game doesn't seem to support more than 3 negative points since I got one off a random event and it didn't do anything. It worked in the overworld but not the battle scene, funny enough.
Still, I had a ton of fun! Definitely worth polishing up a ton more, it has a lot of potential.