What does It expressed a vast power of self-restraint mean?

This is entirely my own personal belief, but I think it means there is more power in self restraint than in letting yourself do what ever you want. You are a better person if you have control over...

implied powers.

Unusally great is size or amount or degree or especially extent or scope familiarity . In information vast used as on adjective is very rare

Implied

the showing of somethig