What mortar to use on exterior building?

We bought a rental unit and its an old stucco?/cement walls. Well between these 2 sections the bottom sticks out a little and the last owner used some kind of sealant to fill it. I was thinking, tear all of that old sealant out and use a mortar to fill in and angle it. Is there any special kind of mortar I should be using? Or will pretty much anything work? We are planning on getting the building painted after this too.

Thanks

 

How is the wall constructed? Is there damage in that area or a water leak above?

It appears there is underlying damage that is pushing the stucco off.

 

Where in the world are you? Where I live this is common with stucco. We know how to prevent it now but when my house was built we did not do it that way.
But to answer your question:
Get off anything that is loose or pulling away and see what you have. maybe you will need some lath and moisture resistant paper before you need mortar.
If you can get it at a big box store get stucco basecoat mix first then maybe you will want a separate coat of finish material. Possibly not since you are going to paint
This https://www.homedepot.com/p/Rapid-Se...0050/202207960
Or this https://www.homedepot.com/p/SAKRETE-...1033/100676107
Or this https://www.quikrete.com/productlines/masonmix.asp
Or this https://www.quikrete.com/productlines/mortarmix.asp
Or this https://www.quikrete.com/productline...wnbasecoat.asp

There are also quick setting mixes that set in ten minutes or so. If the area is small you might opt for one of these.

Let us know what you find when you get the loose stuff off. We can fine tune this