As you may or may not know, the in-game block (and hit) advantage data is wrong for all moves with multiple hits. And all of Deathstroke's specials have more that one hit! If you set the AI to do reversals you can get better data (ex. 19F Tantrum Stance punished Sword Flip, 20F Flip Kick couldn't, punish it, so it's -20). It'll have to do until the frame data is fixed
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Using the AI reversal stuff.
Quick Fire: -17, MB: -17
(Air) Quick Fire: -6 (really low) to -19 (so high that one bullet misses)
Low Shots: -12, MB: -14
Machine Gun: -20, MB: -20
Sword Spin: -7
Sword Flip: -20
Just as an example, you'd need a move with a startup of 19 to punish Sword Flip.