To me it looked like:
Hybrid Loki dominated Imu's second form -> Imu turns into the third form and starts dominating, hence Loki is seen on his knees while Imu is aura farming with one hand in the pocket, proceeds one shotting him.
"Pushed to my limits" = needing to resort to the third form to go all out, not necessarily "Loki was equally matching the third form".