The best replacement for needed is necessary.

The best alternatives to needed are rated as following:
★★★★★  necessary
★★★★  need it
★★★★  required
★★★  wanted
★★  loved
★★  bank account
★  if need be
★  much-needed
★  need to be loved
★  as needed
★  needy
★  much needed
  if needed
  when needed
  being wanted
  twice a day
  as-needed

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Speaking about needed, one probably shouldn't forget about cosigner.

Other search terms related to needed and their ratings are:
★★★★★ cosigner
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