I'm voting for Lady Nagant.
She's just a far better sniper than Mine. Her curving bullets are way beyond anything Mine has done or dealt with.
Lady Nagant's Analytical Prediction is insane. She is capable of firing a curving bullet, before Deku had begun to move, and still land a direct hit on him from a kilometer away. All of this in the middle of the night, and it's raining heavily. Mine lacks the skill to dodge Lady Nagant's first shot.
Mine's blast is a lot easier in comparison to dodge. Her attacks don't curve; they follow a straight line. There are multiple points where she admits that shooting will give away her position. Mine's best chance is to stealth by Lady Nagant, but that's impossible.
Mine's stealth is purely theoretical. She has stealth mastery because she's a member of Night Raid, not because she has shown good stealth.
Lady Nagant's eyes are way better than Mine's, she knows exactly how a sniper would think, she has absurd analytical prediction, she has superior ranged attacks, and superior mobility thanks to the Air Walk Quirk.
Mine's ability to detect murderous intent and danger isn't that much different from Izuku's Danger Sense, and she could work around it. Mine lacks Izuku's mobility, so it'll be even easier for Lady Nagant to land a hit on her. Also, Lady Nagant's superior AP means she could destroy Pumpkin in a single shot.
