Aggressive men can be attractive on a very primal level. Generally, it is unconsciously perceived as being directly related to the physicality they would demonstrate during sex. Which is fine, unless you are their sexual partner and the target of their violence, This isn't the rule of course -- many violent men have a tendency (perhaps rooted in mother-worship) to put their partner on a pedestal and regard themselves as their protector against all threats (even if this is usually demonstrated by beating the living s**t out of some poor bloke who is suspected of 'looking at my bird', and not by actually taking care of their partner's needs in any practical sense).
Some women (and quite a few men) actually enjoy this sort of relationship -- indeed some people have a bit of a 'fetish' for violent men. I suspect (but cannot support with any evidence) that this plays at least a major part in the inability of some battered partners to leave their abusers, because their emotional response to their partner's violent nature is inextricably linked with the reason they love them in the first place, and hence violence directed toward them is understood as being an expression of physical love. Needless to say, such individuals usually come from an abusive family upbringing.
Generally, people who have a more reasonable approach to being attracted to men with the proven capacity for violence tend to pursue men whose violence is expressed in strictly-controlled circumstances. Rugby players and boxers are good examples of these, and also tend to have bodies that are perceived as highly-desirable due to their characteristically developed nature.
Since most physical violence occurs between males, and is closely tied in with perceptions of dominance and submission, it is perhaps not surprising that there is a widespread underground gay subculture of beaters and victims, in which the more usual forms of fetishistic sadomasochism are abandoned in favour of direct physical aggression taken out on a willing victim (who might necessarily be very frightened of the experience he seeks), sometimes to the extent that the victim requires medical attention for his injuries or is permanently altered in some way (a typical example would be by having his nose badly broken and its original shape being unregainable).
This culture is hard to examine, because the 'beaters' tend not to announce their preferences publicly (through usual channels such as dating sites) in case it lays them open to criminal charges, and the 'victims' do not wish to be perceived as vulnerable, but it definitely exists, and devotees occasionally advertise their preferences in contexts devoted to physical combat (e.g., websites such as globalfight.com), frequented by gay men with an interest in violent sports, who may consider taking up violence as a sexual pursuit in its own right.