What Pokemon took you the longest to catch?

[Rubyiris]

Lugia.

Entei took the second longest, only because he was faster than my trapper, and I was way too lazy to level it up.

I eventually just duplicated my Master Ball.

 

[MewtwoMaster2002]

Rare Safari Zone Pokemon on Fire Red. That means Scyther, Tauros, Kangaskhan, Chansey, and Dratini.
Attempting to catch Moltres in a regular Pokeball was hard too because he ends up struggling to KO himself.