Natasha Yar (alternates)

Alternate timelines
In an alternate timeline created when the USS Enterprise (NCC-1701-C) was accidentally sent through a temporal rift from 2344 to 2366, the Federation had been at war with the Klingon Empire for almost 20 years as the Enterprise-C's disappearance resulted in the destruction of the Klingon colony Narendra III. In this timeline, Tasha Yar never encountered Armus and, consequently, did not die in 2364. By 2366, she was an officer in a far more militarized Starfleet than that of the proper timeline.

This Tasha Yar traveled back in time aboard the Enterprise-C and ended up in 2409 after the temporal rift was destabilized. After returning to 2344, Tasha was captured shortly before the ship's destruction. She agreed to become the consort of General Volskiar in order to save the lives of the ship's surviving crewmembers. She gave birth to a half-Romulan daughter, Sela, and died in 2349 while trying to escape back to Federation space. 

In another alternate timeline in which Starfleet ceased to exist after the late 23rd century, Tasha Yar was in a romantic relationship with Ro Laren in the 2360s. 

In another alternate timeline, Yar lived as an anomaly on an Earth circa 2013. This version of Yar was a mutant with telepathic ability. She was used to send the consciousness of the 21st century Kitty Pryde into Pryde's body in the past in a bid to avoid Kang. A Sentinel killed Yar, but not before she accomplished her task. 

Alternate realities
In an alternate reality, Yar was the tactical officer of the US, which was under the command of Wesley Crusher, in 2380. She held the rank of lieutenant commander.

In another alternate reality, Yar was the tactical officer of the United Earth Space Probe Agency vessel Enterprise before it was captured by the Klingon Empire and became the. She was killed while trying to escape from the Klingons. By 2380, Captain Picard was the only surviving member of the original crew.