Last time I forgot sunscreen at a UV index of 10 my skin started peeling of after half an hour so...

Density (and wavelength), rather than total power, is important.

Sun's 1kW/m^2, and even then you shouldn't look directly at it, and being out in it all day without protection leads to sunburn.

It’s not, for an extended period of time. Now imagine it was collimated rather than diffuse.

That's the thing, sunlight is collimated. It only gets diffuse once it reflects of a diffuse surface.

Fair enough, poor choice of words on my part. What I meant was concentrated further (in terms of energy per area) than the typical concentration received at the surface of the Earth.

So there's this thing called sunburn...