WatchDogs 2 has a pesky anticheat software that i don’t think is really needed for singleplayer at all.
It is called easy anti cheat and i bet it will cause just more problems and slow the system down as it steals precious resources needed for the game.

To disable it and remove it alltogether just right click the shortcut (or go into your steam settings, if you have the steam edition) and add the start parameter -eac_launcher
If you have a link to the game, then it needs to look like this:
“D:\Games\Watch_Dogs 2\bin\WatchDogs2.exe” -eac_launcher