AKOM
From Teletraan I: The Transformers Wiki
AKOM is a South Korean animation studio owned and founded by Nelson Shin. AKOM is known for its very error prone... ahem... "cost-efficient" animation and is used frequently for American cartoons. Some shows AKOM has worked on include the Simpsons, X-Men, the Tick, Savage Dragon and Batman: The Animated Series; the company was actually fired from the latter because of their consistently sub-par work.
Since Shin also happened to be the producer of the original Transformers cartoon, Sunbow would start using AKOM beginning with season 2. It's unclear which episodes exactly were animated by AKOM, although it's confirmed that Toei animated 39 of the 49 season 2 episodes[1], which leaves ten more episodes that were shared between AKOM and an unnamed studio from the Philippines[2]. However, as the three episodes The Core, The Autobot Run and City of Steel (which all share the same animation/drawing style, hence suggesting that they were all done by the same studio) are widely considered to be of inferior quality than even AKOM's worst work from season 3, it's highly probable that they were done by the studio from the Philippines, leaving the remaining seven episodes for AKOM.
AKOM's participation would definitely increase dramatically by season 3, where they produced literally half the season (Toei only did 13 episodes, and Call of the Primitives is widely believed to have been done by Tokyo Movie Shinsha). The short-lived Season 4 (the three-part The Rebirth series finale) was then handled entirely by AKOM.
