1. Inspiring fear
   "a tougher and more redoubtable adversary than the heel-clicking, jackbooted fanatic"
   - formidable, unnerving, doubtable [archaic] 
2. Worthy of respect or honour
   "born of a redoubtable family"

See also: alarming, reputable

• Best and Greatest
• best boy
• best evidence rule
• best friend
• best man
• best of all
• best wishes
• best-known
• best-loved
• best-selling
• bestest
• bestial
• bestialise
• bestiality
• bestialize
• bestially
• bestiary
• bestill
• bestir
• bestir oneself
• bestow
• bestowal
• bestower
• bestowment
• bestrew