Hi. First thing, Happy Thanksgiving to anyone celebrating! Second, does anyone know how to change a players speed? If so,how?

The valve wiki says player_speedmod works only in the HL2 series. I'm not sure but if that works it's the best option. If not the console command hl2_walkspeed should be there.

Try a point_clientcommand and set the command to "hl2_walkspeed ###" where your number is there. I don't know what the default is for Portal 2. Don't actually add the quotes in there because it'll break your map.

Using console commands via point_clientcommand is always the last option to choose.
I would, even if Valve Wiki (which isn't always correct) points out it shouldn't work, try to use player_speedmodifier.
And if this doesn't work, there might be an input for "player". Just take a look in your game console. Type "ent_info player" and see if you can find a useable input.

Okay, I don't think I have any good way of doing this. The player was supposed to slow down, but it seems impossible. I tried the point_clientcommand too, it says no such command. The player_speedmod thing increases too rapidly aswell. And I didn't see anything useful with ent_player_info (or whatever it is).

With player_speedmod you set the input "ModifySpeed" with a parameter being a float value. 1 is normal. 2 is double speed. 0.5 is half speed. etc. You don't set it to something really high like the client command would be.

Thank you!!! It worked!!!!