not sure I understand your question, but a lot depends on how you define "lesser mountain"
AFAIK, Everest is not considered a technically difficult climb (K2 is) but obviously it is the highest (for a terrestrial mtn. and few climbs start from the sea floor) and that creates some serious physiological and climate/storm issues
Messner and Habler climbed it by "fair means" - much like most of us would do a day hike...
before them, it was widely believed that the low partial pressure of O2 made it simply beyond human ability - and , for most, it still is w/o supplemental O2
birds, with their superior lung design, can easily fly over the top of it.
another thing about low O2 (and cold) -- they make you stupid - a sub-lethal effect that can have lethal consequences b/c there is little room for error on mtns., esp. on big mtns.
BTW - a favorite question of mine when I hear somebody yakking about climbing is to ask them how many fingers and toes they have; if the answer adds up to 20 (or more!) then they are not a serious climber. I certainly am not.