Lady's Thumb or Persicaria maculosa same family but I've not had many troubles pulling this weed out. Is it as bad as the big knot weeds?
This weed is normal to find in a potted plant out of doors. In the nursery, this pot would be quickly turned on its side, given a big TWACK on the side of the pot, pull the entire plant, weed and soil out of the pot then pull and cut whatever is necessary to remove this weed.
Or more likely someone would see it and jerk it out, at least removing the top growth effectively starting the weed to be starved out. Plants in pots have roots that are easier to manage. Plants are very hardy and able to survive being twacked and their roots mangled (causes more root growth). I've never lost a single plant from the abuse of construction and the necessity for speed.
Your raspberry needs fertilizer. Basic NPK boxed fertilizer, less nitrogen than P and K or equal numbers (5-5-5 or 5-9-7). If you've not used potting soil, this would be a good time to change out that soil and remove that weed. Doesn't take much finesse or gentleness to do this job.
Do you see the dark spot in the center of the leaf? That is where a lady who had dirty gardening fingers smudged this plant dubbing it...Lady's Thumb. Seriously!!