modify,
alter,
change make less severe or harsh or extreme; "please modify this letter to make it more polite"; "he modified his views on same-gender marriage"
decrease,
diminish,
lessen,
fall decrease in size, extent, or range; "The amount of homework decreased towards the end of the semester"; "The cabin pressure fell dramatically"; "her weight fell to under a hundred pounds"; "his voice fell to a whisper"
attenuate become weaker, in strength, value, or magnitude
disappear,
evaporate,
melt get lost, as without warning or explanation; "He disappeared without a trace"
die down become progressively weaker; "the laughter died down"
collapse lose significance, effectiveness, or value; "The school system is collapsing"; "The stock market collapsed"
fade,
melt become less clearly visible or distinguishable; disappear gradually or seemingly; "The scene begins to fade"; "The tree trunks are melting into the forest at dusk"
minify,
decrease,
lessen decrease in size, extent, or range; "The amount of homework decreased towards the end of the semester"; "The cabin pressure fell dramatically"; "her weight fell to under a hundred pounds"; "his voice fell to a whisper"
Weaken -
lessen in force or effect; "soften a shock"; "break a fall"