Unstable when braking

[Sanyo]

Hi,
my Aveo is very unstable when I hit the brake, on the edge of loosing control. Seems that the front left and rear right brakes have much more power.
Tyres are new, brake calipers are renewed, ABS replaced, main brake cylinder renewed, fluid replaced and the problem persists.
Any ideas?

[Sanyo]

Finaly, rear breakes brake stronger then the front brakes. Maybe the main brake cylinder?