How do I remove the large green battery icon from my iPhone screen?

Please go to Settings > Accessibility > Display and Text Size > Larger Text > Turn off Larger Accessibility Sizes. When you have that enabled and the font size large enough, holding on certain aspects of the status bar will cause it to enlarge in the middle of your iPhone’s screen. I believe you are referring to this.

It would help if you could post a screenshot. However, I think you’re talking about the battery widget. Widgets can be removed from the Home Screen the same way you remove apps. Just hold your finger down on the widget, then tap “Edit Home Screen.” Then when the icons jiggle, tap the minus sign in the upper left of the widget.