Ok, so this is my first time doing a calc on my own, so correct me if I'm wrong.
So I noticed this from the profile of Abigail Walker kicking a dude at Relativistic+ speed so I'll be using the same calc but different % of the speed since it was calculated. The Flash has punched/pushed Parademons at Relativistic speed so it makes sense to use the same method.
Flash was able to perceive the Justice League in slow motion who are this fast:
So using this website, http://www.stardestroyer.net/Empire/Science/Relativity.html I'll be doing calcs from 23% as the low end and 93% as the high end as we only accept kinetic energy up to 93% the speed of light since Flash is faster than the League and can time travel by going at near light speed which would be 50%.
So the actor who plays Flash's weight is 72kg so:
Low-End: 23% = 1.783E+17J (7-B)
Mid-End: 50% = 1.001E+18J (7-A)
High-End: 93% = 1.108E+19 (High 7-A)
So what do you guys think?