A former heavyweight boxing champion, Balrog was kicked out of the sport after he brutally killed a man in the ring. After drifting around the world fighting in seedy bars and underground pits for money, he joined the organisation Shadowloo. His undeniable fighting talent allowed him to rise through the ranks, eventually assuming a position as one of the "kings" of the organisation, and he has served Bison (more or less) loyally since.
Balrog is a fairly simple man, with simple pleasures. He likes money, fame, alcohol, women and violence, all in large quantities, all on demand, not necessarily in that order. How actually cruel or malevolent he is is up for some debate, but that his primary motivating goal in life is his own pleasure is not. He's not very intelligent, though possessed of good fighting instincts and an animal cunning that can trip up those who underestimate him. He is loyal to Bison because Bison has provided him with the lifestyle he likes to be accustomed to, but would be quite willing to betray him for short-term gain if he saw an opportunity. He tends to think more highly of his abilities than is actually warranted.
As a fighter, Balrog is not to be underestimated. His strength is prodigious, and few if any in Shadowloo can match him in that area: notably, he once killed an elephant with a single punch. He is also deceptively fast. However, he is somewhat limited by his American boxing style, which only uses his upper body for attack and comparatively neglects the lower. As well, he is hot-headed and doesn't deal well with unexpected events in battle.