Season 2 is underrated. I think it's on par with season 6.
S2 has some excellent episodes, but it also has The Outrageous Okona (IMO the worst episode of any
Trek series), The Icarus Factor, Samaritan Snare, Manhunt, Shades of Gray and four episodes that don't even exist.
Please feel free to mention the episodes that don't in future Episode of the Week posts if they occur after Pen Pals. I'm curious to see what you would consider worse than Shades of Gray to the point that it doesn't even exist.