Excluding the roaming ones, what was your worst experience ever trying to catch a Legendary?
I remember Groudon on one of my playthroughs of Emerald taking over three hours to catch despite having a fair amount of balls going in and it having self-inflicting sleep. Zapdos in Soul Silver I remember being absolute hell to capture as SS was one of my first games and I wasn't prepared for it with a ton of balls + a status infliction move.