3. Clumsiness
Trip Luke or just make him be clumsy and make a fool of himself. It helps if Luke crashes into a couple other objects.
If you study dominos you will realize they fall one after another. That's all you need to know. If Luke happens to crash into multiple other people while you "accidentally" trip him...then you have done us well. You should congratulate yourself for getting this far. Not everyone can master revenge.
Most people (such as Luke) will never be able to get back at you so you should feel free to trip (while he's not looking, of course) to your hearts content. Just try to make him look as ridiculous as possible while you do it. But don't do it every time or he will get suspicious.