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You may want to look up EVs for starters. You can't win competitive battles without them. (Effort Values)

What are you aiming for with your Empoleon? You may wish to make a special attacking variant. Get rid of Mystic Water and grab choice specs or teach it agility over EQ and give it a life orb. Grass Knot might be better than Drill Peck. Modest or Timid would be better natures.

Hyper Beam is bad. Enough said. Salamence does the job you're want your Dragonite to do, and it does it better. But, if you're a dead set on keeping it, replace Hyper Beam with Dragon Dance, and it's up to you whether or not you want to replace aerial ace with fire blast. Naughty is the best nature for it. You can also try for a special set with superpower (rash/mild) or a support (careful/calm) set if you'd like. Dragonite is bulkier than salamence and that along with its movepool are what differentiate it and Sala.

Darkrai is Uber, and many people WILL NOT allow you to use him in battle. At all. Make a replacement for him as he is normally only allowed in Uber play. But Faint attack, is a bad move choice on him (give him a special attack instead), and there is a commonly used clause that will cause the user of double team/minimize to forfeit. If I recall, he also has a 80% accuracy sleep move. Use that over Hypnosis. Life orb is a better item for him.

There are better choices than ninetails in standard play, but again if it's a favorite of yours, go ahead and use it. Replace QA with Energy Ball though :/. You *may* want to replace Confuse Ray with Nasty Plot.

A good infernape set is the Mixape with Nasty Plot. It breaks down almost any walling poke. Naive natured with 64 Atk / 252 SpA / 192 Spe in Evs and a life Orb. Nasty Plot, Flamethrower/Fire Blast, Close Combat, and Grass Knot is simply fearsome.

Torterra isn't suited for OU either, but it has awesome sets and is great and what it can do. If you wanted a physical set, replace Giga Drain and Razor Leaf with Superpower and Stone Edge.

I hope that helped ^^

Actually Will-O-Wisp lowers attack as a burn. As such, it lowers the recoil damage a Pokemon will take when they hurt themselves in confusion. That aside, most people will just switch out when they're confused.