Alternanthera dentata? has a couple of other names like Purple Knight

Mike

Could be. Marked as a Brazilian Red Hots Alternanthera at Lowe's but you know how that goes.

I have this and while it's kind of invasive, it's the one plant that goes through the winter unscathed...when we do have a winter. Sun/shade it doesn't care. Everything else in the garden may look ratty but this plant always provides" beginning of the year" color. For that alone, I don't mind pulling all the volunteer babies.

I have it pretty isolated as you can see so it can't spread. I like it, it adds nice character to this space.