Hello Bluekola888,
Nice to meet you!
Your questions: What skill is "critical" to success in online learning?
Your answer: Skills needed for online learning would be computer literacy, you have to be an active learner, you have to be good in reading and writing. But the most critical that I BELIEVE are CRITICAL is having time commitment and being self motivated.
Thanks for your time and have a great day!
~Rendorforestmusic