Leon (pinstripe), Ada (dress) are special characters which can be unlocked once you obtained S rank or higher on all stages with Leon and Ada respectively. Both characters have a wide range of weapons to deal with most situations.

In my opinion, castle is the easiest stage to play out of all the mercenaries stages, the map layout is easy, you don't need to worry about bosses with instant kill attacks, and there are no dynamite/rocket enemies you need to worry about. However, the armored Garrador can be annoy to deal with, but you can defeat him with a heavy grenade when in mayhem mode. Also, it can be difficult to get a good score.

Ada's rifle can be really helpful in this stage, especially for shooting the parasite enemies from long range. But, Leon's shotgun is better at dealing with the zealots using shields.

With Leon, I did well in the beginning, but messed up a little bit towards the end, I should of used the heavy grenade first instead of trying to switch to the magnum. But, still got a good score at the end. For Ada, the rocket placement could be much better, but I used it earlier on to have extra inventory space for more ammo.

Time stamps,
Leon (pinstripe): 0:04
Ada (dress): 9:08

Condition for the run:
No continuous pausing the game to make sniper/pistol shots.