Maybe this live version of “Nights in White Satin”
Nicky Hopkins multitracked layering of keyboards on “Edward the Mad Shirt Grinder” when he was with Quicksilver Messenger Service builds to an incredible triple-speed climax. OK, a few stray notes follow, but ignore them.
CSN’s “Suite: Judy Blue Eyes” has an iconic ending as well.
“Hush” by Deep Purple.
It starts out with a wolf howling three times, then hits really hard for 6 or 7 seconds with Ritchie Blackmoor shredding his electric guitar, then settles down a while for the verses and the nah-nah-nah-nahs (all sung by Rod Evans), then breaks into an instrumental featuring a great organ solo by Jon Lord, builds into a repeat of the “nah nah nah nahs,” and finally concludes with an earth-shattering and very cold ending on one strong organ blast that will shake your windows.
Loved it in 1968 and still do. In the rare occasion I hear it on the radio I turn it up to 11.
It was such an unlikely song to turn into a hard rock anthem too. It was a country-ish song written by Joe South and recorded by Billy Joe (Down in the Boondocks) Royal originally. I remember seeing Joe South do the song on TV and it was nothing like Purple’s version.
If you’ve never heard this, look it up. In the summer of 1968 it was like nothing we had ever heard before on our local Top 40 station.
As does Ravel’s Bolero.
“Bat Out of Hell” builds to a rather impressive climax.
“Come On Eileen” - Dexy’s Midnight Runners
Another classical piece with a great climax (ahem this one of more lurid “appeal to prurient interests”) is Wagner’s “Love-Death” from Tristan und Isolde.
In “Supper’s Ready” by Genesis, the penultimate section “Apocalypse in 9/8” gradually builds to a furious peak of madness… but then the dark clouds roll away and a spine-chilling drumroll leads into the glorious final section as light bursts from the heavens. For this, Peter Gabriel would change from his 666 monster costume into all-white duds with bright lights on him as he lifted a shining white fluorescent tube.
Speaking of Peter Gabriel (Genesis) made me think of Phil Collins. In the Air Tonight ends really well.
Phil handled “Supper’s Ready” as well, on Seconds Out.
Heart’s “Love Alive”
Zebra’s “Who’s Behind the Door?”
After grunge came along we all had a weird relationship with Guns 'N Roses. But you can’t deny the great climactic power of “November Rain”
You want climax? Check out Oliver Sain’s Soul Serenade. You might get the urge to light up a cigarette after this one.
Thread Winner.
Also, Zip City by Drive By Truckers and Frankenstein by Edgar Winters
We have rapport. 
I think there is ointment for that.
I’d go with most Jim Steinman songs. I’m thinking Total Eclipse of the Heart.
Fairly appropriate for the times. Muse / Knights of Cydonia
“Starship Trooper” is indisputably the thread winner, but the first song that came to my mind is “Light My Fire” by The Doors.
(Which I belatedly see was noted in the OP…oh well.)
I’m a sucker for songs with a great buildup and a long (sometimes tedious) outro…
Deerhunter Desire Lines
Amber Arcades Fading Lines
The coincidence is unintentional