The underdog AI software maker still has a lot to prove.BigBear.ai (BBAI -2.87%) hasn't impressed too many investors since its public debut. The artificial intelligence (AI) software company went public by merging with a special purpose acquisition company (SPAC) on Dec. 7, 2021. Its stock opened at $9.84 on its first day, but it now trades at less than$4.Like many other SPAC-backed start-ups, BigBear.ai overpromised and underdelivered. In the company's pre-merger presentation, it claimed it would triple a ...