Man, Rachel's combo damage is insane. Her holds are one of the most damaging ones in the game. Her throws have great damage even though she's not a real grappler and it's not the fighting style Rachel was created for. She's got a great pressure, great mix-up and many useful launchers (mid kick, mid punch, high kick, low-to-mid string), solid stuns and some great guaranteed options. She's the fastest super heavy, 11/13/14 really isn't that bad (actually her fastest mid is BT 4K that's i12). Her strong knockbacks and air throw gives her good environment control, not telling how scared your opponents is when Rachel brings him near the wall (oh, that tasty 6T ^_^). Having standing OH is great, low OH is a gift from God against characters like Helena or Brad. Do I have to talk about 2K stomp?
Of course Rachel has some weaknesses, like her spacing, neutral game, easy to read strings and negative guard breaks. But with all her strengths they don't matter that much. If you can keep your opponent close to you and read him properly then you're a boss with Rachel.