Slaking and Scizor are probably the toughest. I'd probably use a level 70 flying type on Slaking. Then you'll miss most of his ground-type attacks, although he has some strong un-ground type attacks, too. Use Entei on Scizor, and he should go down easily. Teach your Suicune(in the 60's also) Blizzard to take down Salamence. Entei or Houndoom(in the 60's) would be best against Gardevoir, since Dark attacks effect it a lot. Have your Espeon at level 60 something, too. Then use him to take down Machamp. Use Psychic or Confusion. To take down Slowking, use Raikou, Entei, or Houndoom. Raikou's Thunder, Entei's Bite, or one of Houndoom's Dark attacks(sorry, I forgot his moves) will do the trick.
For Aggron, use Suicune. He should know Surf, so use that on Aggron. If Suicune's on a high level, it shouldn't take to long to finish Aggron off.
Now, back to the pesky Slaking. If your Flying-type failed to do its job, use Entei, Suicune, Raikou, or Houndoom.
If you picked Entei, use Fire Blast.
If you picked Suicune, use Surf or Blizzard.
If you picked Raikou, use Thunder.
If you picked Houndoom, use Fire Blast or Flamethrower.
*For your Flying-type, it's best to use Noctowl because of its Hypnosis*

try 2 find his wekness

Raikou lv:55
entei lv: 55
suicune lv:55
espeon lv:54
umbreon lv:53
flygon lv:56

that answer on how to beat evice sounds good but most of my pokeman are only in the 30's or 50's , how do i get them in the 60's or higher. thanks.
P.S my screenname used to be link1 but i changed it to jonick da man.

U need to train ur pokemon alot.Trie ur best!

Try Mt. Battle. It's probably the most easiest way of leveling up. The first(or a lot, if you're just starting) are easy battles, so it's not really a challenge.
Sorry I can't give more advice. I'd say that you'd trade to Leafgreen, Firered, Ruby, or Sapphire, but you can't since you can only do that once you've beaten Evice...

to beat evace jou most heb jou espion en umbrion at lv 75