since you're using it on orre colosseum which means that you're competing in only double battles, you'll need this moveset:
flareon @ shell bell
fire blast
return
shadow ball
protect
flareon doesn't have many hit points, so the hit points gained from KOing an opponent with the shell bell is sufficient enough so you can save your leftovers for someone who'll actually stick around. without protect, flareon will die, fast. earthquake is on nearly every physical and some nonphysical pokemon in there and explosion is pretty common too. fire blast for power, shadow ball for psychics/ghosts, and return for everything in between. iron tail is an option as well.