The ascent to the top is a little more than 5000 vertical feet. The first 3/5ths are usually done with skins on a consistent pitch. From a prominent rock known as the White Rock some sort of technical tool like ski crampons or boot crampons is usually needed. It's not particularly steep, but the wind rips through here and the snow tends to be firm, especially in the morning.
The summit of Villarrica is an active crater. There is commonly smoke billowing from the crater. In 2016, lava was present, often bubbling up and splashing against the walls. The smoke is toxic and if the wind is blowing from the south, it may not be possible to summit without a gas mask.