Synonyms for Extremity:

n.

a disaster waiting to happen, outside, adventure, threat, havoc, escapade, minefield, danger. arch, calf, foot, big toe, arm, clubfoot, ball, limb, ankle, toe, finger, hand, armpit. base, safety, flash point, politics, corner, crisis, emergency, bump, bottom, back, bevel. explosiveness, severity, austerity, starkness, savageness, gravity, seriousness, ferociousness. appendage (noun)
member.
border (noun)
bounds, fringe, limit, perimeter, periphery.
bound/bounds (noun)
limitation.
boundary (noun)
confines, side, outline.
butt (noun)
bottom, base.
climax (noun)
summit, crest.
edge (noun)
coast, perimeter, ring, outline, curb, periphery, margin, side, brim, frontier limit, precipice, sharpness, fence.
extremity (noun)
border, terminus, brink, brim, edge, top, rim, toe, member, finger, appendage, crisis, end, climax, acme, verge, maximum, foot, zenith, pinnacle, limb, boundary, apex, hand, margin, tip, outside.
limb (noun)
limb.
limit (noun)
border, rim, end, confines, deadline, bounds, maximum, limit, apex, brink, edge, boundary, limitation, cutoff, zenith, fringe, acme, restriction, terminus.
ne plus ultra (noun)
highest point.
summit (noun)
climax, summit, peak, uppermost point, crest, culmination, topmost point, top, crown, highest point, pinnacle, tip, brow, cap.

Other synonyms:

flash point, severity, foot. gravity. austerity. digit
finger.
straits
crisis.
Other relevant words:
back, member, limb, arch, crisis, appendage, severity, clubfoot, foot, emergency, ferociousness, toe, outside, flash point, seriousness, finger, corner, hand.

Usage examples for extremity

  1. Yet even in this extremity their well- bred and dignified behaviour came to their aid; for they soon either obtained their freedom, or gained the confidence and respect of their masters. – Plutarch's Lives Volume III. by Plutarch
  2. At this extremity of ill- doing she did not altogether blame Denas. – A Singer from the Sea by Amelia Edith Huddleston Barr
  3. When the mustang halted his trot beside the other horses Carley was in the last extremity – The Call of the Canyon by Zane Grey