Sometimes artists start out on a high level and improve. The point was made by an exemplary show of Alice Neel’s early paintings from the 1930s and ’40s at Zwirner, an elaboration on her acclaimed retrospective at the Metropolitan Museum of Art. And sometimes artists start better than they end up. Another singular show was “Maria Lassnig: The Paris Years, 1960-1968,” an valuable glimpse of the early career of the Austrian painter at Petzel (through Dec. 17). I’ve always found Lassnig’s mature figurative paintings arch and repetitive. Her climb to maturity was a delightful exploration of line and color infused with animation and humor. These early works are, to my mind, better than what came after.