In hammer: not really, though you could use some custom signage at the end of a level to show if people achieved the achievement(s) in your map.

chickenmobile wrote:
To actually create achievements, you would have to create a mod. A real, game code editing mod.

And because the code for portal 2 isn't published it is impossible at the moment.

CamBen wrote:
or, you could create vgui that is parented to the player's veiwpoint that displys after the trigger

In order to create a vgui you need to add game code. Just putting it out there...

chickenmobile wrote:
To actually create achievements, you would have to create a mod. A real, game code editing mod.

More than just a mod, you had to have a mod that was given accss, unless they give out Steamworks access to any schmuck these days. Back when I remember doing this stuff you had to have access to the Steam achievement server.