What are the characteristics which make someone either an excellent or a “nightmare” travel companion for you, you in particular, not people in general?
Spontaneous, interested in most things, willing to try new things, willing to adjust plans if something particularly interesting crops up.
Someone with a good mix of street smarts and awareness of nature, particularly awareness of the “comfort zones”, and aggravation levels of large or vicious or poisonous animals.
A nightmare would be someone unaware of our situation, and unthinking of the needs of others.
I have been in some very dangerous situations, and always got out alive, mainly through displaying respect for and interest in other people; and sometimes that respect involved not noticing them when they clearly did not want to be noticed.