Resistant weed in my flower beds
This looks like Canada thistle, an invasive perennial broadleaf weed.
The easiest option may be to cut the thistle at the base to exhaust the root system. This effort will have to be repeated.
If possible, another option is to paint the thistle with a paintbrush using a nonselective herbicide containing glyphosate. Do not let it touch your desirable plants as this kills everything. See more resources on our web page http://extension.umd.edu/hgic/topics/canada-thistle