The best replacement for regret is remorse.

The best alternatives to regret are rated as following:
★★★★★  remorse
★★★★  guilt
★★★  sorry
★★★  regrets
★★  rejoice
★★  ragret
★★  apology
★★  rejection
★★  repent
★  repentance
★  resent
★  lament
★  declines with regrets
★  regretted
  relief
  rue
  shame
  rsvp

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Speaking about regret, one probably shouldn't forget about jason evert.

Other search terms related to regret and their ratings are:
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