Angel is relatively lower in the tier lists. This can possibly be attributed to the complexities of her own unique mechanics, which require you to even know proper positioning to get combos to even work with her. If you are able to do this, her combos can be as damaging as anyone else’s–it just makes people consider using less complex characters that can compete with similar damage.
This combo guide goes a long way in explaining how to make her competitive. While not only going over her best buttons, it also goes over her Unchain mechanics–a set of moves with link into each other similar to target combos, but are varied and require you to not repeat inputs in any way.