to make (a person) less angry, calm

satisfy, pacify

to settle a dispute (between two opposite sides, opinions etc) by acting as the chosen judge(s)

achieve settlement

to agree with, behave in the same way as, (generally accepted rules, standards etc)

adjust, adapt

to act to obtain agreement; to produce (something) as a result by doing this

try to bring to an agreement

to make (anger, punishment etc) less serious or severe

check, diminish, lighten