The knee is your most powerful killing move by far, but the B-Air is also pretty strong. U-Air can also be used to kill at very high percentages. Make sure you D-Air punish when possible and follow up with a knee for the kill, but do so sparingly and only when you know you can land it, otherwise you're going to be punished hard for your mistake. Also, Grab -> F-Throw -> Knee/D-Air works in certain situations, though not always, but has proved effective in my matches. Use Side-B very sparingly as it's rather slow and easy to get punished. The way I use it is to retreat and then suddenly Side-B towards them. Tends to catch them off guard if they're hellbent on chasing you. Always follow up Side-B with a N-Air, U-Air, or the knee (Which one you choose depends on their damage). Falcon kick is a random, but effective move to use, but only when it's not predictable from a mile away. As I said, use it randomly on an overly aggressive opponent or even as a tech chase in some situations to catch them off guard. Hell, I've even used it to kill going from on-stage to offstage when they are directly horizontal with the ledge and at a high percentage.