Which church had more problems than any other congregation Paul dealt with?
The church in Corinth had more problems than any other congregation Paul dealt with. The context explains that Corinth was that church, and Paul addresses their carnality and lack of spiritual depth in 1 Corinthians 3, contrasting them with the Thessalonians who quickly grasped deep truths.
Les explains that Corinth was the church that had more problems than any of the other congregations Paul dealt with. In 1 Corinthians 3, Paul says he could not speak to them as unto spiritual but as unto carnal, because they had not gone into the deep things. Les contrasts them with the Thessalonians, who, despite Paul's short time with them, had covered the whole gamut from the rudimentary to the very deep things.