Complex sentence: Nick is loud, unkempt, and extremely unsophisticated; despite these tremendous flaws, he has at times exercised an inexplicable romantic power over Carla (which, years before, resulted in their marriage).
Split into simpler sentences: Nick is loud, unkempt, and extremely unsophisticated. Despite these tremendous flaws, he has, at times, exercised an inexplicable romantic power over Carla (which, years before, resulted in their marriage).