>>27034

Not OP, but I'm pretty sure it's Source Filmmaker. There are a lot of guides and tutorials for creating animations with it. The time and effort required to get to a decent level are probably measured in tens of hours, depending on your general proficiency and learning ability. The amount of learning materials is pretty vast, but even so reaching a similar level of quality as OP would take a very significant amount of effort.

You need to find the models from around the net yourself, which isn't that hard. Any guro/gore stuff like OP's requires tricks and editing the materials yourself, because 99% of models don't have built-in gore or such. Only a very limited amount of Mortal Kombat models do.