Is an extremely competitive person, even in futile things, insecure and suffers from low self-esteem?

Yes, I've encountered people like that. The ego has grown to a pathological state - whereby they cannot stand the idea of anyone doing anything better than them, or before them. Definitely moving in to psychiatric disorder territory.

The couple of people I've met over the years who were that way inclined, were utterly disgusting weasels. Betraying people's trust in order to 'win' is nothing to them - so don't befriend them

That could actually go either way.

You have to have self confidence to be competitive, so that counters low self esteem.

Some people are more competetive and have a stronger urge. And drive to better tbemselves. That's one of the instinct things i think that helps. I agree they shoulsnt be a sore sport or whatever they call it. And should be trying to just get better at it and help others gst better to while trying it. No need to try and get others down. Wrong state of mind to have. Low self esteem? Lol.. No... I dont think so. Plus the indtincts thing loke i was saying.. 

No. Being driven, ambitious,  and competitive are character assets, not for the cowardly, incompetent, or those stoned most of the time.