Incapable of failure or error
Foolproof
Valuable; much loved or valued
Treasured
Sb who is intelligent but not fashionable or popular
Geek
Real
Genuine
Intuition
Gut feeling
Difficult, strong, hard
Tough
Competition for the same objective or for superioruty in the same field
Rivalry
Caring only about yourself and not other people, even if sth affects others negatively
selfish
Person apparently sensitive to things beyond the natural range of perception
Psychic
Answer which is intended to be amusing rather than serious
Light-hearted response
Need to (re)pay sb
Owe
Only interested in yourself and your own activiries
Self-centered/Egocentric
Easy-going, having a happy personality
Good-natured
To look for, search
Seek
To include or affect sb/sth
Involve