Then I'll contradict Stratoquarius' comment (as someone who has kept two oscars to adulthood in the past and is growing out a third one right now), and say that I think it is a normal oscar that just happens to have a slightly different body shape from the others (oscars come in a pretty wide range of shapes, just depending on genetics). So no, there's definitely no reason to cull a healthy fish, but whether you want to keep or sell it is your decision (personally, I'd keep it; it looks like it has good potential as far as coloration).