I have MacBook Pro (late 2013) and I'm considering getting Dell U2515H QHD monitor. The MBP has two Thunderbolt ports.
The monitor supports DisplayPort and DisplayPort 1.2.
Which adapter I need to get in order to use the Dell U2515H with my MBP?
The MacBook Pro Thunderbolt ports are fully compatible with DisplayPort so as long as you have a DisplayPort cable, there is no need for an adapter.
I own 2x Dell U2715H myself. Dell is so nice to deliver their display with the needed cable. Working like a charm and I love the displays.