Are you really really very keen to save the tooth? One way I see is to perform an apicoectomy first followed by Repeat RCT. This will save the tooth. But it requires a good surgeon, a good hand doing the RCT and lots of patience at your end. This would be the simplest way to save the tooth and yet have good prognosis.

If you wish to take a chance and save the tooth you can visit an endodontist and try for re-rct. But the prognosis remains guarded . Or second option is get the tooth extracted

The prognosis to save the tooth doesn't seem to be that good so I too suggest the removal of the tooth as early as possible.as there is huge abcess in the periapical region which requires emergency removal of tooth with broad spectrum of antibiotics and analgesics to be followed with .            Other option would be re rct  can be tried with many sittings of caoh dressing in between to resolve the lesion n wait n watch for the healing process to occur .

No ! Any other treatment won't be possible . It's a case of root canal failure . And long term side effects are very rare . So don't worry much . You should go ahead as soon as possible

Other options include re-rct but It doesn’t seem to work in your tooth because there is separated file in one of the root , plus there is ample amount of abscess present . Best is to get it removed as soon as possible. Your doctor suggested you the right outcome and treatment.

Absolutely u need extract(remove)Ur tooth as soon as possible.

You can go to a experienced endodontist who has microscopes and take opinion whether it can be saved or not.