Greer Grant Nelson, better known as Tigra, is one of the most popular unused characters in
Marvel Comics, yet the character seems to have a
cursed existence. Nearly every
comic that has had her as a feature character has bombed, and any
cameos have been extremely short-lived.
Tigra was introduced in the 60's as a new costumed hero (not Superhero) named The Cat. She was an unremarkable character, very similar to many that both Marvel and DC fielded during the late 60's and early 70's, and as a result, her title comic, The Cat, had a very short, unpopular run. After cancelling The Cat, Marvel created a new comic, called Giant-Size Creatures. In its premier issue, The Cat was shot by a nameless minion of HYDRA, and nearly died. She was rescued by a race of cat-people, and transformed into a living incarnation of one of their legendary warriors. She now has superhuman strength (Able to lift approximately 5 tons), agility, endurance, and heightened senses. She is also furry - orange with black stripes, like a Bengal tiger. Tigra can change out of her feline form at will, but prefers to stay as Tigra most of the the time.
After the short run of Giant-Size Creatures, Tigra was unused again until Marvel created a series called Marvel Chillers, in which she was the headline character. Alas, Marvel Chillers, too, was cancelled after only 7 issues. After that, she remained unused for several years, until Marvel decided to add her to one of their headline comics, The Avengers. Her stay with the Avengers was brief, and was written out of the story rather quickly.
Once again, she remained unused for many years, until Marvel decided to create a new comic - West Coast Avengers. This would be both a high point and a low point for Tigra. It was her longest continuous use as a character, but she was treated as a secondary character from the beginning. Later in the series, the writer John Byrne actually made her "devolve" into a feral, mindless creature, and was forgotten by other writers when John Byrne moved on to work on other titles. She was eventually cured, almost as an afterthought, in an Avengers Spotlight story, during which time they gave her a tail to match the rest of her feline appearance. Since then, Tigra has appeared now and then in various other comics, such as The Avengers, Spider-Man, and The Fantastic Four. Her most recent appearance, as of this writing, was in the Avengers Infinity limited series.
Tigra is a tragically underused and abused character in the Marvel Universe. The writers never gave her a solid personality, but just made her flirtatious and flighty, with occasional tendencies towards feral behavior. As a result, her apparent intelligence varies wildly depending on who writes her, and writers tend to ignore her in favor of more developed, dynamic characters.