Need advice on moving a cable with a steel beam and stairs in the way
I'd be looking at a larger re-run to address the illegal junction box. You might be able to avoid this hurdle altogether. Aside from that, I'd do this:

Open up a little more drywall so you can get your drill and a drill bit in each of those openings.
Drill from below at about a 10 degree angle to the right, and to a depth of about 3&quot; into the triple beam above. Roughly center the hole in the wall depth and keep it centered on that plane.
Drill from right to left through the triple beam, 2 inches up, intersecting the earlier hole. Angle slightly downward to ease the bend where the bores intersect.

I'd use a 3/4&quot; or 7/8&quot; bit. That should be forgiving enough yet not be absurdly large in terms of framing damage. It's important that you align the holes carefully. Then pull a light wire or string through as a fish line. Feed the cable gently though the bend to avoid sharp kinks.