It's actually mostly a South Asian thing, not really a European thing. There are plenty of immigrants from areas where these attacks have been popular in Europe, though especially in the UK, as acid seems quite popular as a means to mutilate in countries like Bangladesh and India. That doesn't mean only immigrants commit these specific crimes, of course, but it's how these types of attacks became prevalent in Europe.

Acid attacks seem particularly popular in London, though most of the world's acid attacks still take place in Asia.

I'd say the European equivalent to gun violence would be knife violence, which is why the British police has cracked down on all things capable of stabbing others (and resulted in silly news articles about policemen posing with confiscated screwdrivers and such, because those are becoming alternatives for knives in areas where knives get confiscated effectively).