Hardest raid boss to catch?

Lugia

I think Lugia is because the Trick I use is to wait till he attacks and then throw the ball. I hit Tyranitar every time with that strategy however Lugias attack makes him move up and down so its harder to hit the target.

Tyranitar is so easy compared to all legendaries...to the point where I pinap it unless it's a 2070+

He does attack very frequently so time your throws after one attack (unless he chooses to double attack)

My vote goes to Moltres. He's so far away, he changes elevation, and attacks extremely frequently. Plus, he has a lower catch rate to begin with.

Caught 8 Tyranitar out of 9.
But only 1 out of 7 Lugias (though I hit it quite well) and
only 5 out of 13 Moltres (which I am really bad at).

So my vote goes to Lugia and Moltres.

All legendaries, each for different reasons, but never Tytar. He's so easy with patience

Lugia

Tyranitar is easy, caught 5 out of 6. Only 1 out of 6 for Lugia, definitely the toughest. Although 1 of those Lugias that got away was due to the game crashing and not letting me try to catch it. Even still, I can barely hit Lugia with half my throws, it's always moving around so much. And when I throw the ball when he's ending an attack, half the time it just falls to the ground uselessly for no reason. The other half, he goes instantly into another attack, so I miss anyway.

Lugia by far!

Ttar 8 for 9 (6 with pinap)
Lugia 1 for 9
Articuno 4 for 8
Moltres 2 for 6

I've had worse luck with Muk (1/2) and Gengar (1/2) than TTar. Ttar is easy if you are patient.

Do you have the 'dark' medal?

Tyra: 9/14
Arti: 9/12
Lugia: 7/13
Molt: 5/11

Based on my numbers, Moltres is the most difficult. Then followed by Lugia, Ttar, Articuno.

Tyranitars are much easier than the legend birds. Patience is a must. Never rush to throw balls. Focus on every single ball thrown. Take your time. They ain't going anywhere unless you run out of balls. Set desired circle size for great/excellent using the ball grab/release method. Throw curve ball during attack animation. The only skill that one needs to pratice is consistent accurate curve balls. I got over 200 normal raids and over 80 lengendary raids under my belt. Overall catch rate on level 3-4 raid bosses for me is over 95%. Overall catch rate for lengendaries is over 70%. Moltres I'm 17/22 - 77% rate. And many consider Moltres the toughest bird to catch. I've sharpened my skills for Moltres and it's paying off in dividends.

Ttar is by far the easiest to catch compared to any legendaries. Among legendaries, lugia by far the most difficult to catch. Articuno and Moltres are about the same level of difficulty although I have been more successful with moltres