Diablo 3, it really is like popping bubblewrap, it is mindless, no need to save, always something shiny and just addictive.
Of course if i want more substance, then an mmo like elder scrolls online where you just quest around and explore is quite relaxing too (group content / raids are not part of this relax mode though ).
But as someone mentioned, save points and modes which you can't simply quit or stop at any moment, that tense me up (losing progress phobia) . So if i want to relax in Destiny, then patrol missions are an example of a shooter which is relaxing (open world, and just doing whatever you want, yet still making progress).
I must add, while i feel open world sandboxy games are relaxing, they MUST still give a sense of progress. I get bored just running around / driving around with no purpose, hence diablo being a weird combination of messing around yet you still gain gear and levels..
