You need to get nvidiaInspector, select the game profile and set the frame rate limiter to 60 or the refresh rate of your monitor. The supersampling trick above just tries to put so much pressure on the GPU that it renders less frames. On beefy GPUs, even that isn't enough. Giants' demands on the GPU are too puny.

make a shortcut and add a framelimit to the destination of the game

Example:
"C:\Program Files (x86)\GOG.com\Giants – Citizen Kabuto\Giants.exe" -framelimit 100

Also you can get the multiplayer patch 1.497 on Giantswd.org and dont forget to add a " - " before " framelimit ".

Cheers

If somebody is interested on multiplayer matchs i can call you guys through steam when we are about to do one!

Id/watermelomachine my nickname is buster

heres a match i recorded with some buddies /watch?v=IQXBfU-Nl7o

Thank you so much for this! Tried just about every other suggestion and nothing worked. Game was completely unplayable but this fixed it! Jumping right in to this awesome looking game.

This worked perfect, at first i thought this was going to be a hassle and almost didn't bother (troubleshooting game issues is becoming tiresome these days). Anyway I just had to play Giants again so here I am letting people know that using Nvidia Inspector is actually hassle free and worked great for me (I have a 75hz monitor so I just matched the framerate).

Thanks very much! :)

*Edit* I'd also recommend downloading the latest (unofficial) 1.5 patch as it has nice graphical improvements and some bug fixes.