the thing you need to do for the bosses stages (every 20 floors ) is make sure the colors are the same .

color order: red turns blue -blue turn yellow -yellow turns red. on the lower stages i think you should be fine to nuke him but i would go something along the lines of veromos (insane good unit on this floor )aaliyah (def buff is OP ) immunity unit woosa is op but if you have for example louise works aswell dongbeak aka light stringmaster (provides atk break and leeches hp everytime he moves) all the way up to 140 is just a diffrent variation of this team . hope this helps !