Answer:
Two in a whole and four in a pair. Six in a trio you see. Eight's a quartet but what you must get is the name that fits just one of me.
Some try to hide, some try to cheat, but time will show we always will meet.
I make you weak at the worst of all times. I keep you safe I keep you fine. I make your hands sweat and your heart grow cold. I visit the weak but seldom the bold.
I start with T end with T and within me is T.
You heard me before and then again. Afterward I die until you call me again.
What made Cyclops quit teaching?