yes ruthless, determined? there are better words. in this thread the original idea was psychological intimidation factor of the appearance of strength-as is achieved by bodybuilding/weightlifting. many impressive looking body-builders are not actually tough, having built their muscles in a controlled environment and rested and eaten well afterwards, while hard labor and determined martial arts training develops perseverance and forbearance, toughness, mind body and spirit.
meanness as i meant it is the ability to switch on an animal sort of savagery, giving a person who seeks inner peace the ability to strike viciously in a sudden self defense encounter. i do not advocate becoming a 'mean person', but cultivating in yourself the ability to 'do mean things' when your own moral code allows it, to save yourself. if you lack the mindset to cause harm when needed, you'd better be really good at what you train to do. it is possible to defend without harm, but requires greater skill. for the purposes of pure self-protection, especially excluding firearms which make it so much easier (but still very possible that unprepared persons will be unable to shoot to kill),you gotta be willing to get mean and dirty, however 'unbecoming'. just my opinion, once i might have been more confident in my physical prowess to defend without causing harm, but i am not young anymore. for me success would likely hinge more upon my willingness to be brutal from the outset, to whatever degree the threat involved made appropriate-no more, no less. i'm not a mean person, but can be pretty horrible if i need to be.
sports are not the same conversation. when i think of tactics for self-defense, i am not thinking about what works for professional athletes and highly-trained martial artists, but for average people with enough provocative interest to train a bit for the however unlikely eventuality of being attacked. mindset training and general awareness can't be overlooked, those of us who train for many years may take these things somewhat for granted, but many people fail to defend themselves becasue they hesitate, or pull their punches, out of an instinctual reluctance to 'be mean'. and yes, this comes from fear, an instinct of self-protection that does not always lead us to making the best choices, and must be redirected through training to develop appropriate responses to replace reactions.