I think the real danger lurking in the shadows is behavior that triggers an overt and deliberate cyber attack. None of the real "players" want anything that remotely looks like a shooting war because everyone loses the minute primers start getting dented.
Launch a cyber attack that shuts down a major power grid or a communications hub if you really want to see some uncontrollable global destruction.
Use the interwebz to "Turn off" all the power in Tehran - even if it is only for a few hours. Global markets will go batshit crazy and people will start rioting in the streets. Think of the recent protests in Hong Kong but then inject a little bit of Stephanie Rawlings-Blake level "we also gave those who wished to destroy space to do that as well" and see how it impacts the entire planet.
Turn off the power in Los Angles for just 45 minutes during rush hour - and try to convince me that 63 million clint0n voters wont march on DC with torches and pitchforks.
...they wont want retaliation brought on Iran or Russia or China - they will turn all of that hatred inward.
Just like the tankers are Trumps fault now - not surrendering to Iran's bully tactics are why those tankers were hit; the peace loving Iranians are just signaling OrangeManBad. Turn off the internet for 20 minutes so modern day america cant rant and rave about the President Trumps Tweets and every purple haired vagina hat wearing nut job in the US will be at the steps of city hall looking for blood. Not because a belligerent force attacked the USA but because OrangeManBad. THAT is the clear and present danger that I see from my foxhole.
Shooting wars aren't as much of a threat as they used to be - nobody wants to get into a shooting war because its just so damn messy. Now that Twitter has been weaponized the next "real" war will be fought in binary. Halting the the global Twitter Feed would be worse than crossing the streams on a Ghost-Busters proton-pack...
Try to imagine all life as you know it stopping instantaneously and every molecule in your body exploding at the speed of light. Total protonic reversal.