Tiger Shark, Abyssal Hunter

Two connive triggers on one body is the whole idea: one fires on the way down, another fires every time he swings, so the +1/+1 counters accumulate without any external filtering. Each connive that pitches a nonland grows the 2/3 while it digs, which means the body scales up precisely when you're finding your action. The evasion clause is the conversion mechanism. Connive only matters if the attacker keeps eating chump blocks, so the activated ability that makes him unblockable turns the counters you've been stacking into guaranteed damage. The portion of the cost keeps the package flexible: it casts in mono-blue, mono-black, or full Dimir, the right call for a creature whose loop is card-selection-into-aggression rather than color-dependent value. What keeps the loop from running away is its cost structure. Every card drawn off connive is paid for with a discard, so the growth is real but incremental, and the unblockable activation wants the same mana you'd otherwise spend refilling your hand. He is a threat that improves through combat, each swing another card seen and, when you pitch a nonland, another counter placed, but only for a hand willing to keep attacking into the pressure that setup.