This really depends on what exactly you mean by 'power'. If you simply mean the greatest resulting effect of the trait, then Tyler is absolutely right - it's our will to survive and procreate - mostly the later.
If you're thinking in terms of the most emotionally 'overpowering' trait - it differs from person to person, so you can't really make an accurate generalization. The will to survive is perhaps the best guess - but I've known people that don't generally value there lives all that much. Personally, it would definitely be my will to survive - I think that my will to life is far above average at least, and that I would live to be a hundred on your typical deserted island situation - alone.
I wouldn't say 'hate' or 'anger' or 'love' because they are all reactionary emotional responses, in many cases not applicable. Nor would I call 'stupidity' a trait - it's relative of course. I wouldn't say that the most 'powerful' quality of chimps, afterall, is stupidity. Saying something like that, is, ofcourse sentiment.
So to make an all around generalization, I'll go with Tyler: the will to survive/procreate. Not many people would react against the norm in some situations. An average guy stranded on an island with a supermodel... ? Add in that she really dislikes you, makes for an interesting scenario.
I'm rambling.
-Distortion