Star Trek: Endgame Fiction Vs. Reality

What Happens In The Episode:

We have to undergo a fair amount of speculation as to Icheb's fate in 2404, where he is neither seen nor mentioned in the alternate timeline. Considering the weight given to characters who met a tragic end, like Tuvok and Seven, Icheb's lack of presence would indicate that no such tragedy has befallen him.

It's likely he joins Starfleet, with a promising future given his significant intellectual gifts, but otherwise we just don't know.

What Really Happens:

Unfortunately for Icheb, we 100% know what happens to him following Admiral Janeway's sledgehammer to the time stream.

Icheb does indeed join Starfleet once Voyager arrives in the Alpha Quadrant, and manages to rise to the ranks of Lieutenant. Whilst on leave, Icheb aids his former crewmate, now Fenris Ranger, Seven of Nine, fatally sucking him into the orbit of Bjayzl and Borg component black marketers.

Finding Icheb harvested and in unbearable pain in Bjazyl's lab, Seven is forced to euthanise the young Lieutenant who she had once seen as a surrogate family. Had Admiral Janeway not changed the time to avert Seven's death, she never would have linked Icheb to Bjayzl, and he may have never met such a horrific and tortured end.