Neglect of terrapins and turtles (and tortoises), basically all chelonians, can cause issues with their shell which can become warped and disfigured. They often need additional heat (heatlamp, heatmap), a certain kind of lamp to supply (I think) UV for the shells, plus calcium in diet for obvious reasons, plus other specific dietary needs. Turtles I had previously pooed in the water, which therefore had to be changed a couple of times a day. They can take quite some care overall.