an opportunity to pass away, or escape, or be lost

friendship or enmity cannot begin or last till both sides do their part of work

it requires two hands to clap

it takes two to make a quarrel

one hand alone cannot make the clap sound, it takes two to make a quarrel

make helpless, dominate, persuade to yield, subdue

it takes two to tango

gain practical experience of, get it done through, get out of (someone's) hands