I'm stuck on the elite 4 lucian!?

Question

I keep getting beaten by medicham. Any ideas?

This is my party

Darkrai lvl 50 hypnosis, nightmare, spacial rend, roar of time

Vespiquen lvl 50 defense order, attack order, power gem, heal order

Infernape lvl 51 close combat, mach punch, ember, flame wheel

Alakazam lvl 50 calm mind, hidden power, psybeam, psychic

Whiscash lvl 51 surf, earthquake, zen headbutt, ice beam

Luxray lvl 50 spark, crunch, strength, thunder fang

(and by the way darkrai isn't from cheating. I got him from an event in England)

Answer 1

you got to level your pokemon up 10 more levels

also you should get a ghost pokemon like gangar