Database: superhero
Question: Which publisher published the slowest superhero?
SQL: SELECT T2.publisher_name FROM superhero AS T1 INNER JOIN publisher AS T2 ON T1.publisher_id = T2.id INNER JOIN hero_attribute AS T3 ON T1.id = T3.hero_id INNER JOIN attribute AS T4 ON T3.attribute_id = T4.id WHERE T4.attribute_name = 'Speed' ORDER BY T3.attribute_value LIMIT 1