I assume you mean the adventure from the back of the DMG?
This is pretty exciting out of the box in my experience. When I DMed it the players weren't expecting a fight of that calibre after the previous encounter (which had all the hallmarks of being the BBEG fight) and so went in somewhat unprepared. In the fight we lost one PC and the rest had to bug-out.
When they came back I added in some new encounters as a lead up to the final one, representing kobolds who had previously been out and about coming back and fortifying their home. These new fights were tough for the party (needlefang swarms are way dangerous) and they were still quite tired before their second attempt at the final encounter. In this second attempt they played things in a much more tactical way, with a paladin and fighter doing tag-team marking on the big-bad whilst keeping the other PCs out of its area effect power. It was still quite a tough fight but totally do-able. After the first, failed attempt the players had thought the encounter was impossible!
Just try to keep the enemy moving around and avoid things turning in to a straight exchange of blows. The players will be have their adrenalin running if they weren't expecting the last fight, without you having to do anything special to make the encounter memorable.
Have fun,
Cheers
Dan