Aside from Sergei, none of the other assassins are shown to bleed when V kills them. This is especially apparent with X, who was shot twice in the torso and his dead body clearly displays no visible wounds.
After killing the second assassin, the protagonist walks down a hall and kills the third. However, the body of the previous man is not visible.
The confrontation between V and Sergei displays his jacket at different positions. The first shot of Sergei depicts him with his leather jacket zipped up. When we first see him on the ground, his jacket is open, revealing his shirt. Finally, he is shown with his jacket closed after V kills him.