Deathstroke himself could not really answer that question. In truth, he had never felt that he had ever truly loved anything all that much.
If it was a love of sports, then his football results had actually been pretty good back then. If he had chosen to go to college, maybe he really could have made something of it. But he gave it up and chose to join the army instead, even lying about his age to enlist. In other words, he had not even finished high school. He had probably only attended for a year or two before going off to serve.
If it was a love of being a soldier, then he could have simply stayed in the military. He was in excellent physical condition, and his relationships with people were decent too. If he had chosen not to accept the experiment and had slowly climbed the ranks in the army, he could probably have become a lieutenant colonel or a senior colonel by now. But he had still come out to work on his own.
If it was a love of being a mercenary, then in fact, when he first entered the line of work, it had been because the human modification had some side effects, making him violent and bloodthirsty. He could not quite control himself, so he could only go to the battlefield to vent. Later, he met The Intermediary, who thought he was very talented. Deathstroke also felt that it could both solve the side effects and make him money, killing two birds with one stone, so he agreed. And once he started, he kept at it until today.
Most of the experiences in his life had not been choices he made out of love. Thinking about it now, it really was somewhat bizarre.