overpromise

verb

1. To promise more than is delivered.

   “We don't want to overpromise.”

   “So rather than posh skin creams that overpromise, a good brow job gives instant results.”

   “Hope Hicks, one of the President’s longest-serving aides, warned Parscale against touting ticket request numbers, reminding him that the number one rule in politics is not to overpromise and underdeliver, a source familiar with the matter said.”

   “"[...] If the economy has tanked... then we don't want to over-promise and under-deliver."”