I will pick the Cuban Missile Crisis.
Description: The Soviet Union had been placing ballistic missiles on Cuba which were capable of hitting the US in a matter of minutes and threatened the safety of US citizens. The US would respond by placing its own ballistic missiles in Turkey and Italy near Russia, which raised the tension levels between the two countries. Such ongoing tensions were a result of differences between ideologies, where each country tried to spread its own ideologies to other countries and fought for control over different territories through proxy wars to stop each other from spreading their ideologies. With the missile crisis, the tension would be raised to an all-time high, however, after diplomatic negotiations between Kruschev and Kennedy, both agreed to dismantle their missiles to prevent an all-out war. This event would lead to a hotline being installed between Moscow and Washington to prevent future escalations.
Hope that helps!