ThunderCats (2011) series does not have a second season on Netflix

The high-quality animation provided by Studio 4°C in Japan made it significantly more expensive than other Cartoon Network offerings at the time. Toy Sales:

Many streaming databases erroneously split the 26-episode first season into two “volumes.” On DVD, Part 1 contained episodes 1-13 (ending with the destruction of Thundera), while Part 2 contained episodes 14-26. In several regional Netflix libraries, these “Parts” were mislabeled as “Season 1” and “Season 2” due to metadata errors. Consequently, thousands of viewers finished “Season 1,” clicked “Season 2,” and did find 13 more episodes. They never realized that was the end of the run.

Their relationship and Tygra’s complex backstory were slated for deeper exploration.