Character

Strength of character does not show itself through ubiquitous aggression. Through continuous seeking to belittle others, or cut others down. Contrary to predominantly popular belief, it is not a propensity for competition, nor eagerness to condescend, but kindness compassion, and eagerness for collaboration, which act as infallible outward indicators of inner strength. 
This is not to say that kindness is "right," any more than aggression is "wrong."
It is to say that the conscious and ongoing choice to walk a path of compassion and collaboration is one which requires much more personal fortitude, than does a path of thoughtless competition. 
Neurochemically speaking, the ability to show kindness and openhearted consideration towards a person whose character, lifestyle, or beliefs differ from your own, shows a greater than average level of neuro-plasticity. Conversely, a personal propensity for unprovoked combativeness or conceit, commonly indicates an overabundance of neurotransmitters associated with trauma and stress, which decrease the brain's ability to adapt to and accommodate environmental shifts.
Put another way, if kindness towards others is not your baseline, there is a strong possibility that some form of inner turmoil is inhibiting you from evolving and thriving to your utmost innate capacity. 
This is not esoteric dogma or obscure philosophy. This is not "pie in the sky" morality. 
This is biochemistry. This is neurology.

-e