The Assassinater is an elite Sniper that was introduced in the 1.4 Patch, and produced with Prestige Stars in the Prestigious Academy. The Assasinater also requires a SpecOps Center in order to be trained. At Rank 1, the Assassinater is on par with a Rank 3 Marksman, so once the Assassinater reaches rank 4, in theory, it will be the best trainable Sniper unit in the game.
Compared to other sniper units, the Assassinater differs from them greatly. He provides Partial blocking, and his "sneaky" nature gives him high defense and dodge, which increases each rank, unlike the other snipers. The Assassinater also has a low healing cost, requiring whereas other units at this level typically require .
Despite being the best Sniper (as of 2.3 Patch), the Assassinater is only available to players who have reached max level and earned an additional 30, not including the 10 needed for the Prestigious Academy.
PvP is a different story however. A higher rank Marksman is more desirable since both the Marksman and Assassinater's damage is comparable. However, the former has a lower PvP Unit Value, which will match the player against equally lower-valued armies (typically meaning less tanks, where snipers' rifles fare better). The tradeoff is the before-mentioned worse defensive stats of a Marksman.