Sister of Captain Britain, Betsy Braddock is the psychic X-Man known as Psylocke. Originally just a telepath, Betsy ended up switching bodies with a deadly assassin that allowed her to become the psychic ninja she is today. Psylocke uses her telekinetic powers to manifest a "Psi-Knife" and her trained ninja skills to slip into the shadows and cut enemies down with her martial arts and katana skills.Marvel Source
Start by pulling with Psionic Vortex, which also adds 10% vulnerability -> Then immediately use Tsunami Slash. Say "bye" to all the trash...
For anything still living, pop Psionic Projection (or Shadowstep) to enter a stealth state -> then quickly use Assassinate -> after that, spam Kirisute Gomen while it's still buffed from the stealth (lasts 6 for seconds, minus the time it took to cast Assassinate). Whenever possible, use Ethereal Butterflies for massive extra damage (it's worth noting that butterflies seems to take you out of stealth, so try not to use it right before you're going to use Assassinate).
By now you should have stocked up a full bar of Psionic Energy (and used up a lot of Spirit)... So it's the perfect time for a Psi-Strike beatdown. Beyond that, it's a rinse and repeat.
When you need to rush in, or out, go with the Psi-Thrust as it will trigger the DOT from Telekinetic Prowess AND the buffs from Psionic Resilience.
Psi-Knife & Psi-Bolt are melee & ranged basic attacks to fall back on if you're desperate for Spirit/Psionic Energy.