Support and contrast ( verbal practice)

GRE Verbal Problem Solving
1

At once __ and severe, genial and __, she is a bundle of ________: an enigma people find both fascinating and vexing.

what are the support and contrasting words for all the three blanks

  1. at once (support)
  2. ?
  3. : (support)
2
3

The second blank uses the same clue as first blank. So 2. at once (contrast).
Not that ‘at once’ is contrast , not support.