poor thing. It's trying to live, but it looks so sad. That's a pretty small pot for that size shrub. I don't know what you can do at this point. It may survive a hard pruning, but I don't think that will improve the appearance. I could be wrong...

Since new growth is emerging from the base, hard pruning of the upright growth is a real possibility. It will, however, take some years for the plant to regrow enough to look acceptable. Perhaps a better alternative would be to cut back the upright growth only slightly and remove the two long branches with bare stems on the right in the bottom photo. This would avoid the hacked look of hard pruning and allow the lower growth to fill in over time.

Clay pots are usually good for rhododendrons because the evaporation through the clay helps keep the roots cool. You do have to be careful that the drainage is good, however. Soggy roots deprived of oxygen will die and rot. If there really is no room in this pot for additional root growth, a larger pot is probably a good idea.

I agree with everything mainegrower said, but in my opinion it's no doubt long overdue for a new pot...as Lily suggests. In the US a residential complex like this would probably have at least a large pneumatic dolly/hand truck that could move around a 500 lbs item. IMHO get the biggest planter possible if you intend to keep the plant for a long time.

Area looks a bit dark, possibly...in Paris, at least, even a potted standard type rhododendron like this would probably do best with a couple hours of morning sun. They do have "hot spells" in August but they aren't really that hot by US standards. A larger pot would be safer in a sunny area, too. It will bloom better with a bit of sun, but the watering will need to be more precise of course. Not too much, not too little...just maintain a consistently level of moisture. A thin layer of organic mulch will help with that.

Final advice: when repotting, aggressively break up any circled, tangled or constricted roots. Thick ones may need to be cut if they are really in a knot.

David, the OP has said that is a new pot, recently repotted. I would have liked to have seen larger, or at least wider. Long established healthy rhododendrons would recover from a severe pruning, that one - recently moved and root pruned being moved into a pot - might not.

Hi all, thanks for the comments and tips. I've decided to let the rhodo rest for a bit then take it out and plant it in my partner's grandmother's garden. There is a very nice spot for it where it can get the space it needs. Frankly, I didn't want to keep it originally since it's in such poor shape, but a couple of people didn't want to see it go; I just need to convince them it's for the best. I think it deserves a better retirement.

How much time should I let it rest before I move it to the garden? Also, should I prune back the branches now or wait until after it's been transplated again?

The sooner you can get it in the ground the better. Rhododendrons transplant well, especially from a container. Just rough up the roots a bit and cut off those stubs.
Mike