could it be Pokeweed?

Probably an Amaranthus.

HTH
chris

Here is a link that might be useful: {{gwi:320535}}

Yea...Pokeweed seedlings don't generally have that appearance.

It does look like a red-stemmed amaranthus seedling to me, but the color in the pic is kind of washed out, so it's hard to tell for sure.

If it's a red-stemmed amaranthus, it will soon develop a feathery read cluster of blossoms, very similar to a celosia. (It's in the same family.)

This little guy is not photogenic, LOL
This is a little better photo of him.
{{gwi:320536}}

It does resemble a Celosia, have you had them growing
in or near your garden before? Perhaps a neighbor's garden.
They can reseed from year to year.
HTH
Chris

I have never planted any in my beds.
Not sure about the neighbors?

An Alternanthera maybe

Just thought I would let you know it is a Celosia.
It started growing a red fizzy bloom.

yes is celiosa!!!