Well, anyway, since I could pick 6 people, I will said the 6 requirement to be the perfect Assassin, and then ask for you guy have to find them:
Perfect Presence: An Assassin need to have the most appropriate presence for the most appropriate place. Just like how no ninja wear black, as it would constract to darkly in the night, a lack of presence as all times can sometimes spell danger. The best kind of presence, is the presence where instead that one couldn't feel, but a presence that
wouldn't be feel out of place, perfectly blend in with the world itself, and thus could always naturally ignored.
Best Candidate:
Koishi Komeiji
Perfect Identity: Your body, your mindset, your philosophy, your history, your soul...All of it should be the most fitting, the most appropriate, for the identity you're in. The alibis must be flawless, the proof, unrefutable. The past must always be the truth, even if it's a lie. Be a presence that spontaneously appear out of no where, and at the same times is always there, like a universe sprout out 5 minutes ago.
Best Candidate:
Keine Kamishirasawa
Perfect Information: "There're no such thing as truth that could be hidden forever", is the motto of your life. As if possessed an omniscient eyes, you know everything you need to know during your mission, from the opponent's identity, his strength, his habits, his love ones, his surrounding, his world...The space, the time, the world itself, all is in your grasp, and none shall escape your sense.
Best Candidate:
Ruler (Sherlock Holmes)
Perfect Weapon: The best weapon an assassin need to have the three negative: Unable to be trace, unable to be discern nor derive, and unable to be stopped. As if stricken by bad luck, an unfortunate and inevitable "accidents" will always seemingly fall upon them, and as if you're holding Fate itself in your palm, there's no choice for them but Death.
Best Candidate:
Perfect Movement: Infiltration, Escape, Blend in place,...An assassin need to be able to move to anywhere, live at anyplace, and escape from any obstacle. They could walk in for the first times, and it's as if you have own the place itself, having the perfect grasp of the "World" around you, and be able to become the freest being they could possibly be, unable to be stop.
Best Candidate:
Perfect Will: "Wait, and Hope". The world never follow your whims. Accident and mishap always happen. Your enemies is beyond your expectations, and your allies betrayed you...Even so, still hold to yourself the unbreakable will to kill, the resolve to finish, the drive of living, the strength to surpass the impossible. The will to hold on to hope in the darkness of the world, create unthinkable miracles, and kill the unkillable...That's perhap the least assassin-like, yet the most important attribute you could have.
Best Candidate:
Avenger (Edmond Dantès)