General Competence:
* Competence
* Ability
* Skill
* Expertise
* Proficiency
* Dexterity
* Talent
* Aptness
* Efficiency
* Effectiveness
Specific Skills:
* Cleverness (for intelligence)
* Wisdom (for judgement)
* Leadership (for leading)
* Resourcefulness (for problem-solving)
* Creativity (for originality)
Positive Attitudes:
* Dedication
* Diligence
* Perseverance
* Motivation
* Confidence
The best antonym will depend on the specific context in which "ineptitude" is used.