Abort a long-running future Apex job
To abort long running batch, future or scheduled Apex jobs, you may use System.abortJob() from the Developer Console (execute anonymous window) and pass the job id to this method. Ie., system.abortJob('7078000000XXXXX')
Here's the link to the Salesforce help page with more information: Abort a long running future Apex job (salesforce.com)