Whats the least amount of pokemon you used in the Elite Four?

Three in Diamond which was Torterra, Staraptor & Azelf.

One, I remember curbstomping E4 with Blastoise in LG and with Sceptile in Emerald.

I remember defeating the Elite Four (or close to defeating it) with just a level 70+ Fearow and a level 50+ Feraligatr in my very first game (Silver). I wonder how I even made it that far! xD

Probably 2 in Pokemon Emerald, Rayquaza (lets face it the game is begging you to just use him, lv70 before the weakest pokemon league of all time) and Swampert to cover anything Rayquaza couldn't kill.

I did a solo-run of SoulSilver with a Quilava (not a Typhlosion; I gave it an Everstone) and it was around Level 70 when I got to the Elite Four ;-;

I was able to defeat the E4 in the original games with just a Lvl. 87 Snorlax and only used an other pokemon so I could revive it.

When younger I used to play the games with only the starter pokémon(I didn't really like training), so I've beaten the elite 4 with only 1 pokémon in gold, crystal(Typhlosion), ruby(Sceptile and Blaziken), fire red(Charizard and Venusaur), emerald(Sceptile and Blaziken again), pearl(Infernape) and soul silver(Typhlosion), maybe I used other pokémon for healing.
Now I enjoy having a 6 pokémon team so I don't do it anymore.

I did a solo-run with Blaziken on HG a few months back. Was actually a lot easier than i first expected.

I think I actually did it with one on Emerald. Just Rayquaza. This was back when I had no other games, no Xbox, no life etc. so Rayquaza was lv.100 and I was just getting everything else to as high level as possible using exp. share (mainly due to my belief that Kadabra, Seadra etc. had to evolve eventually, right?).
So yeah, I've done it with one. And probably only two moves - Fly for Dusclops, Outrage for literally every other pokémon.

My Lv. 90 Mew could do the entire Hoenn E4 (with Steven as champion) by itself, without taking a single hit... Everytime. The first time I did it i nearly cried with joy.

A single level 100 Articuno in Pokemon Blue, I believe. Back in the day, when G/S were still the newest games, a lot of time was spent leveling up all of the Pokemon in the games me and my brother had (actually, it was mainly my brother who did this. He even set a goal to catch all the Pokemon in his Gold version, and get them all up to 100. He never actually did get that far, but he did get an impressive amount up to level 100, only to lose them all due to the internal battery running dry D:), and I just wanted to try and beat the E4 with a single Pokemon. Articuno was one of my favourite Pokemon back then, so I just went with that one. It took a few tries, but after some time, I did do it, and I was pretty happy about it. Never actually done anything like it ever since, but then again, I haven't gotten a Pokemon to level 100 since Silver either :p

A level 100 Blaziken I had back in the day was able to do the entire elite four of Hoenn on his own. It was really a masterpiece to watch, no overheat was used that day. Although, I think I did the Sinnoh league with a lower level Pokemon by himself, not sure though.

I successfully vanquished the post-game Black Elite 4 with only a Level 100 Empoleon several times. It did get difficult on the odd occasion (particularly with Marshal) but it was smooth sailing for the most part.

Hmm, the only one I remember is in Diamond. I only used a Empoleon and a Staraptor. They weren't overly leveled or anything and I had to revive them a lot, but they came through in the end. =)

if your refering to a first Pokemon League clear, my least was 4 members in Platinum consisting of only: Infernape, Floatzel, Luxray and Staraptor

If not 6 Pokémon then 5. But never any less.

Back in the day? Only Blastoise in Gen 1. Nowadays I try to have six Pokemon by the time I reach the E4, even if I have to deposit some of them afterwards.

Fire Red.

Tyranitar.

That is all.

Blastoise in Red, Crystal and Emerald. It was fun, he destroys most things.

In Emerald, I used 3 Pokemon to defeat the Elite 4. However, that was post-game. I had enough time to train my team to a high enough level. I know I used Latias, but I cannot remember the other two.

The only time I considered beating the Elite 4 with a couple of Pokemon during the actual story was in HG. I could only use 4 Pokemon, as it was a part of a challenge. I used Blaziken, Absol, Altaria, and Metagross. Lance's Dragonites gave me loads of trouble, but I finally beat him.

I should really try a Solo challenge sometime, hmm.