Critically
(Adjective)
Synonyms:
  1. pressingly
  2. instantly
  3. imperatively
  4. necessarily
  5. indispensably
  6. momently
  7. requisitely
  8. essentially
  9. primarily
  10. crucially
  11. capitally
  12. exigently
With great urgency
(Adverb)
Synonyms:
  1. desperately