Welcome to Smogon! Take a moment to read the Introduction to Smogon for a run-down on everything Smogon, and make sure you take some time to read the global rules.
I don't really notice anything broken about Tera – it's super predictable most of the time, and to be honest, it doesn't do much. Really the only time I struggled against Tera was a Tera Ghost Rusted Shield Gholdengo, and even then the main reason I couldn't beat that team was because of the...