I got you all beat. Latios in Ruby. Full health. One Ultra Ball. Caught.
A friend of mine has you beat, although that is very impressive. One blue, he caught Mewtwo with one standard pokeball, at full health with zero status ailments. I've done the math and it's perhaps a 1/5000 chance that would happen.
In Firered, I stocked up on about one hundred Ultra Balls to catch Mewtwo. When I started the battle with it, I paralyzed it and knocked it's HP down to 1 or 2. Threw an ultra ball. Got it on the first try.