* Arsenal were seeking unlikely comeback
* Theo Walcott fired Gunners ahead
* Robert Lewandowski levelled from penalty spot
* Arjen Robben and Douglas Costa killed off Arsenal
* Vidal completed humiliation
* Arsenal exit at last 16 stage for seventh consecutive season
LONDON, March 7 (Reuters) - Bayern Munich ran riot with a second successive 5-1 hammering of Arsenal to reach the Champions League quarter-finals 10-2 on aggregate at a stunned Emirates Stadium on Tuesday.
Trailing 5-1 from the first leg and striving to become the first team in Champions League history to overturn such a deficit, Arsenal led at halftime through Theo Walcott's goal.
But once Robert Lewandowski equalised from the penalty spot and Arsenal skipper Laurent Koscielny was sent off, the Bundesliga leaders ran amok against their dispirited hosts.
Robben capitalised on a defensive mistake in the 68th minute before substitute Douglas Costa curled in a third to send Arsenal's fans streaming towards the exits.
Bayern were not finished though and Arturo Vidal struck twice as Arsenal slumped to a seventh successive elimination at the last-16 stage in humiliating fashion. (Reporting by Martyn Herman; Editing by Toby Davis)