That's Henbit, Lamium amplexicaule. I doubt you planted it, unless you're collecting weeds. It hasn't 'come back'. It's an annual.

Yes, I thought it looked like Henbit, but why then would it grow in the exact 3 locations I planted a particular purple flowering plant last year, and nowhere else? Maybe Lamium?

I don't know why it's there but it's 100% Henbit which is a Lamium species. Perhaps there were seeds in the soil of last year's annuals.

Curiously, though native here, I've rarely ever seen it.

Ok, definitely Henbit. There must have been seeds in transplant soil, because the whole area was disturbed, but only the locations where I planted that particular plant grew the Henbit. Thanks you all for your help!

It could be impure seed and only the weed sprouted.