Putin usually retaliates by shelling Ukrainian cities and spreading more lies by trolls.
Curiously enough, most (but by no means all) of the shelling of Ukrainian cities in that conflict appears to be the work of the Ukrainian government's forces, for the simple reason of target availability. It's not that Russians are morally opposed to flattening a city, all its inhabitants included; it's just that the Donbass civil war was/is fought in what effectively are suburbs of major cities on the pro-Russian rebels side, with entirely predictable consequences.