Delete Twitter Direct Messages. Go here: https://twitter.com/messages?since_id=0 Then paste this stuff into your Chrome inspector console

delete twitter DMs.js

// delete console.log
querySelectorAttempt._timerIDs = []
function querySelectorAttempt(selectors, callback, _attempts){
  if (!Array.isArray(selectors)) selectors = selectors.toString().split(/\s*,\s*/)
  console.log('querySelectorAttempt', selectors, _attempts)
  if (_attempts == null) _attempts = 20;
  var elements
  selectors.forEach(function(selector){
    if (elements && elements.length > 0) return;
    elements = document.querySelectorAll(selector);
  })
  if (elements && elements.length > 0) callback(null, [].slice.call(elements))
  else {
    querySelectorAttempt._timerIDs[querySelectorAttempt._timerIDs.length] =
    setTimeout(function(){
      _attempts--
      if (_attempts === 0) return callback(Error("ran out of attempts: " + selectors))
      querySelectorAttempt(selectors, callback, _attempts)
    }, 100)
  }
}
function deleteTwitterDM(callback){
  while (querySelectorAttempt._timerIDs.length) clearTimeout(querySelectorAttempt._timerIDs.pop());
  
  querySelectorAttempt(['.dm-thread'], function(error, buttons){
    if (error) return console.error(error)
    buttons[0].click()
    
    querySelectorAttempt(['.dm-delete'], function(error, buttons){
      if (error) return console.error(error)
      buttons.forEach(function(button){ button.click() })
      querySelectorAttempt(['.js-prompt-ok'], function(error, buttons){
        if (error) return console.error(error)
        buttons.forEach(function(button){ button.click() })
        callback && callback(null)
      })
    })
  })
}

function deleteTwitterDMLoop(){
  deleteTwitterDM(function(){
    setTimeout(deleteTwitterDMLoop, 500)
  })
}
deleteTwitterDMLoop()