It is a bit hard to understand which achievement you are referring to exactly, but I am going to take a guess based on your recent games and your progress with Deadeye seal. You are only missing the "Sub Machinist" medal from all weapon types, so I am assuming this is what you mean.
The medal requires 3 kills, not 2 as described in the requirements. It is a bug with the description.
If this is not what you meant, please provide a screenshot of the achievement for clarity. Imgur/similar sharing site works best.
English
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Maybe it's my translation problem