Forretress@Leftoves:- Spikes, Sandstorm, Double-Edge, Explosion
Scizor@Leftovers:- Double Team, Agility, Baton Pass, Steel Wing
Umbreon@Leftovers:- Toxic, Confuse Ray, Meanlook, Double Team
Kingdra@Leftovers:- Attract, Dragonbreath, Surf, Icbeam
Typhlosion@Leftovers:- Flamethrower, Earthquake, Thunderpunch, Rest
Machamp@Leftovers:- Curse, Cross Chop, Earthquake, Rock Slide
Your party is great, but I do think that using two Steel types isn't so great though. And, having all of them hold Leftovers means that you either cheated, or you had to do a lot of trading to get them, because you cant get that many in one game.
And I think that you should give them a power-up item instead (example: Typhlosion should hold charcoal, and Kingdra should hold Dragon Fang or Mystic Water)