The best replacement for challenge is opportunity.

The best alternatives to challenge are rated as following:
★★★★★  opportunity
★★★  problem
★★★  challenge
★★★  threat
★  obstacle
★  support
★  ironman
★  difficulty
★  gulong ng palad
★  bituing walang ningning
★  gp4
★  running man
★  dare
★  veloflex
  up for the challenge
  beachbody ultimate reset
  tough mudder
  challenge for cause
  jungleman
  fitnessgram
  rwc 2011
  struggle
  google
  antonius
  leed
  ariat heritage

Your alternative for challenge is not listed? Suggest!
Speaking about challenge, one probably shouldn't forget about sarcastic words.

Other search terms related to challenge and their ratings are:
★★★★★ sarcastic words
★★★★ advocare
★★★ catalyst
You have in mind a companion for challenge and it is not yet here? Propose!



Google Trends

Scale is based on the average worldwide traffic of challenge in all years. Click on graph for more.
challenge
opportunity
problem