1st one to come to mind was Howard Davis Jr. One of the most talented fighters in history as far as pure skill. But basically fought one way. Another in my opnion is believe it or not Shane Mosley. Mosely was very Robotic in the ring even in his prime. And if his "A" plan was taken away, he never adjusted or had a plan "B". He then got this " Dear in the headlights " look and became hesitant. In all his fights he never came from behind to win a fight. At least not that I remember.
When you think about it though quite a few fighters could be considered one dimensional. But that one dimension was so overwhelming they were almost impossible to beat and went on to ATG greatness because they perfected that one thing they did well . Take for J Frazier. Everyone knew what Frazier would do well before they fought. And I'm sure they thought they had the perfect fight plan to beat Frazier and his one dimensional attack.... But how many were able to implement that plan and actually beat Frazier? Same can be said of Marciano, Foreman, Dempsey, Foster, Trinidad, Mugabi, etc
Orlando Canizales. Extremely skilled, but always boxed the same, and to the level of his opposition. The only difference was he would really speed up when he needed / wanted.