Answer
The final Space Shuttle mission led by astronaut Scott Kelly was STS-134. Launched on May 16, 2011, the primary objective of this mission was to deliver the Alpha Magnetic Spectrometer (AMS), a particle physics experiment, to the International Space Station (ISS). Throughout its 16-day duration, STS-134 marked the 25th and final flight of the Space Shuttle Endeavour, culminating in a successful landing at Kennedy Space Center on May 31, 2011.