Cough, ahem, No Man's Sky...
According to Steam I'd played around 40 hours, but in reality most likely <10 hours active and stupidly left the game idling a couple of nights which racked up the hours.
I tried to get a refund from Steam and was refused, I then tried a charge back from PayPal and Steam stepped in and more or less told me that if I continue down this road I'll be locked out of all my games.
A few lessons learned:
1. Don't pre-purchase games
2. Wait a couple of weeks for real gamer reviews
3. Avoid Steam/digital distributions for higher value games.
This has certainly soured me from buying anything costing more than a few quid on Steam.