"Self-effacing" means not claiming attention for oneself, retiring and modest. The opposite would be someone who has an exaggerated sense of self-importance, which is "conceited". "Aggressive suggests a forceful or competitive nature but does not directly contrast directly with "self-effacing". "Lousy" is slang for something bad or poor in quality. "Unfriendly: describes a lack of warmth or kindness but not in direct opposition to being self-effacing.