A "bittersweet victory" means achieving success or winning, but feeling a mix of happiness and sadness because of certain circumstances or sacrifices made during the process. Full definition
But this is clearly the most bittersweet victory for Clegg: his seat saved but his party decimated, his leadership in question, his cabinet seat lost. (theconversation.com)
Man City would go on to win the match in regulation, but the announcers of the game called it a «bittersweet victory» for the Citizens after losing on of their best scoring threats. (caughtoffside.com)
Democrats won a bittersweet victory in two key state Senate races in Tuesday's special election. (vox.com)