Feat.
It's hard to see from this angle, so I went into Source Filmmaker and pulled up the file for Meet the Soldier, which gives us a much better angle.
Image 1. (Ignore the pixel count)
Image 2. (Ignore the Red pixel count)
Distance Travelled[]
Centimeters Per Pixel: 180.34 / 118 = 1.52830508475 cm/px
Rocket Travel Distance (Green Line): 935 * 1.52830508475 = 1428.96525424 cm, or or 14.2896525424 meters
Soldier Travel Distance (Dark Blue Line): 213 * 1.52830508475 = 325.528983052 cm, or 3.25528983052 meters
Time[]
Meet the Soldier is 24 FPS, and the feat happened in 15 Frames.
Seconds Per Frame: 1 / 24 = 0.04167 s
Total Time: 0.04167 * 15 = 0.62505 s
Speed[]
Rocket Travel Speed (In Video): 14.2896525424 / 0.62505 = 22.8616151386 m/s
294 / 22.8616151386 = 12.8599837858x Difference
Soldier Travel Speed (In Video): 3.25528983052 / 0.62505 = 5.20804708507 m/s
Soldier's Actual Travel Speed: 5.20804708507 * 12.8599837858 = 66.9754010697 m/s. Subsonic
Results[]
Soldier's Travel Speed: 66.9754010697 m/s. Subsonic
tfw this makes Soldier faster than scaling with hammer units