Help Identifying Basement Rough-ins
The one on the left appears to be a for a vanity sink. Though sinks usually connect to 1-1/2&quot; pipe, anything below slab level is usually upsized to 2&quot; for clog avoidance and easier cleaning. You'd reduce it above floor level. It's positioned to be either in the wall or in the cabinet.
The center is the toilet. 4&quot; stubs are often used so that you can install an inside (hub) flange, reducing the inlet to a standard 3&quot; toilet connection. You'd cut it off and install a cement-in flange over your flooring. It's positioned to be centered 12&quot; off your finished wall surface.
The right one is for a shower. They're typically left with a box around them so you can fine-tune position for the pan or tub you select by adding a trap assembly. The pail is simply a concrete form/barrier.
If you're going to eliminate the shower, just cut the stub below floor level, cap it, and fill in the boxed area with concrete. There's nothing to bust up.
Disclaimer: Plumbing is like a box of chocolates. You never know.... The pipe on the left could be a vent for the toilet. I'd run some water in each, with them all opened up, and see what you see (or hear).