Echo is the lastest new character that has been added to Overwatch. It was teased in a trailer released few days ago. The character seems fine until you realize that...its not fine.
The ultimate for Echo is the ability imitate other hereos in Overwatch. This ability makes it too OP to a great extent. It also lets her to charge up the ultimate ability of the character she's copying 650% faster than normal, which means she can absolutely decimate an enemy team given the right circumstances.
Even if Echo dies during her ultimate usage ( imitation of another hero ), she spawns back at the place of ultimate use with full health, that makes defensive ultimates of other hereos pretty useless against Echo.