1.)On the Bespin Platforms, Kamino, and The Rhen Var Citadel stages it is possible to blow Jedi Heroes off of the platforms and/or cliffs by using grenades/grenade launchers or heavy blaster cannons shooting near their feet.
2.)Any Stage where a speeder bike is available. You can speed through Jedi Heroes at full speed and it will kill them instantly.
3.)To kill a Jedi hero instantly just play a level with starfighters and land the starfighter on top of them.
I got this from http://cheats.ign.com/ob2/068/617/617662.html