Last updated on December 4, 2020

Anyone can report abusive behavior directly from a Tweet and the instructions are as follows:

  1. Navigate to the Tweet you’d like to report on twitter.com or from the Twitter for iOS or Android app.
  2. Click or tap the  icon on the right.
  3. Select “Report”.
  4. Select “It’s abusive or harmful”.
  5. Then, you will be asked to provide additional information about it. Perhaps Twitter will ask you to select additional Tweets from the account you’re reporting to evaluate your report in a better manner.

Source: https://help.twitter.com/en/safety-and-security/report-abusive-behavior