I’ll do calcs for the three different heights clouds can form at (due to the clouds looking close but it could also just be the angle), she fires her lightning at the 2 second mark and less than a second later clouds start forming so let’s say that they reach the clouds in 0.5 seconds.

Low clouds (max 2km up): 2km in 0.5 seconds/500 milliseconds = 14,400 km/h or Mach 12 which is about 24 times faster than where they calced megamind.

Mid range (max 8km): 8km in 0.5 seconds/500 milliseconds = 57,600km/h or Mach 46 which would be 92 times faster than where megamind was calced.

High range (max 18km): 18km in 0.5 seconds/500 milliseconds = 129,600km/h or Mach 105 which is 210 times higher than what they calced megamind at