What is this please?
Does it have a distinctive odor when the foliage is crushed?
I have it too!! Yes it smells minty, has square stem. I thought maybe it bee balm, but it is one plant, no runners.
Either bee balm or lemon balm?
I'm not convinced the two pictures are of the same species of plant. The leaves seem quite different to me. I can't see the stems on the second one to compare.
I don't think they are the same. The first one looks like it would hurt to pull.
The top picture looks like a stinging nettle. Does it have spines on the mature plants? If so, that's what it is. Will keep on stinging after it touches your skin.
Roundup, more that one application or dig them out. Roots are an underground trailer and are hard to get rid of.
The top picture isn't stinging nettle. Apart from the different appearance I'm pretty sure the OP would have mentioned being stung.
Anyway - marthastoo appears to have lost interest in her/his question.
Top pic looks like Lantana.