Dave goes to the hospital to visit Night Bitch. He said "I'm Kick Ass" , while removing his glasses with his left hand. In his right hand, he has flowers. When he is sitting on the bed, a second later, he is wearing his glasses again. He had no time to do that.
The ID number of the police car bombed with a propane tank by Mother Russia has conflicting numbers. When viewing the license plate, the vehicle number is 79I5. In the overhead shot, the number on the trunk is 0729.
When the lawn mower crashes through the police car's windshield, the windshield breaks into long shards. Windshields are made of two glass sheets sandwiching a plastic inner lining and do not shatter like regular glass.
When Mother Russia blows up the first police car, the blast is so powerful that the vehicle is flung high upwards, yet the tree right next to this event doesn't even sway in a breeze. In reality, even a small explosion will set off a shock wave that's visible for quite some distance.
When Mother Russia is destroying the police cars, she puts a lawn mower on the trunk of one and then backs that car into another one, which launches the lawn mower into the windshield of the police car. That model lawn mower needs to have the control handle held down, otherwise the motor turns off.