Throwaway-ticketing, no issues with it at all. You can (and some would say should) cancel the return, doesn't matter what reason.

Last year I flew HYD-SIN-MNL on Tigerair on a return itinerary, then decided to fly MNL-HKG-BKK-CCU-HYD on other carriers instead of back via SIN. I just didn't show up. 3 months later had another flight on Tigerair and had no issues, so it's not like they had recorded anything against me on their system.