Hello!

Of all the playable characters, Red Hood is the easiest when it comes to invisible predator challenge maps. When you are done with your objectives, just perch yourself on a gargoyle and shoot everyone.

The easiest character for invisible predator maps is whoever has the easiest objectives (and I have no idea who that might be considering the sheer number) since fulfilling those objectives is often 95% of the challenge and the rest is just silently taking down the remaining thugs.