Admissions officers care way more about *what* you're taking than *how* you're taking it, so an online community college course in calculus will actually look solid on your application. They see that you're being proactive about filling gaps in your school's offerings, and that matters. The format itself - online vs. in-person - doesn't carry the stigma you're worried about. What they'll evaluate is whether the course is rigorous and whether you perform well in it.
The main thing is picking a reputable community college and getting a strong grade. If it's accredited and recognized as a legitimate course (which most community college offerings are), admissions committees will take it at face value. Actually, showing initiative by seeking out calculus when your school doesn't offer it can work *in your favor* - it demonstrates you're serious about academics and willing to put in extra effort. Just make sure the college is legit and the credit transfers cleanly to your transcript if that matters later.
One heads-up: verify that the course will show up properly on your transcript and that you understand how your target universities view community college credits. Some schools list them differently or have specific policies, so it's worth checking their admissions pages beforehand. But the online delivery itself? Not an issue at all.