Without a doubt, Unravel is one of the most graphically impressive 2D platformers. Unfortunately the game uses prominent depth of field effect (with film grain) that blurs the background , it is only possible to switch between "high" and "low" in the settings:
Reviewing this I can not see any options to reduce it beyond low.
I've freshly installed Unravel to see if it generates any additional config files where you could change something like
depth of field = 0.
However this doesn't appear to be the case and it looks like high and low are your only two options.