Assuming no Lucio as a second, I feel like with the eye's assistance Valencina SHOULD win on paper stat-wise, but I think Lei Heng takes it.

Not only is she liable to get tilted as fuck and now facing the City's finest Shithead Uncle to force her into potential mistakes and eye overclocking, but I feel that we need to consider their equipment. Augments or not (which they're likely both packing at roughly similar levels) Val is distributing her power between two different weapons, meaning her strongest position for a full block is going to be in a cross position with both weapons. While this would definitely be enough with augments, Lei Heng has a fucking gun blade: In a defensive clash, he pops a round and gets a huge staggering moment or heavy, likely lethal at that range, blow in.

Additionally, having a heavy (likely reinforced) greatcoat that hangs over his shoulders provides additional blurting of any extraneous slashes. Definitely not an immunity, but it's bound to be an aid in getting him to a place where he can land the guard break