차라리 is the closest to 'rather'; It is used when you are comparing an action, choice or whatnot to another, and it implies that although the two(or more) choices are similarly unfavorable, one of them are what you would 'rather' choose.
"아 비오네. 어떡하지? 기다릴까?" "Oh it's raining. What should we do? Should we wait(till it stops)?"
"아니, 학교에 늦을 바에는 차라리 비 맞고 갈래." "No, I'd rather get wet than to be late for school."
오히려 can be used when you describe something that is contrary to the expectations or common senses.
입추가 지나면 좀 시원해질까 기대했는데, 오히려 더 더워지네. *입추 is one of lunar seasons. it means "entering autumn".
I thought it will get cooler after 입추, but it only gets hotter.
90년대의 휴대전화와는 다르게 최신 스마트폰들은 오히려 크기가 커지고 있다.
Unlike the cellphones in the 90s, the newest smartphones are getting bigger in size.
대신 is pretty much the same as 'instead'.
나는 새 카메라 렌즈 대신에 드론을 구매했어.
I bought a drone instead of a new glass for my camera.