I think dogecoin is a very profitable altcoin.
Yeah. Dogecoin used to be a very profitable altcoin, but nowadays it is not worth it to mine it anymore. Also, there seems to have been little movement in Dogecoin development as I have checked Github earlier and last update was last year.
Still, I think that right now the most profitable alt coin is ETC. It would be best to mine some of these just for the profits, while it lasts since I have the feeling that ETH may prevail in the long term. Anything could happen with these both chains (ETH & ETC) so only time will tell whenever one of them will truly survive.
Now, I am looking into mining altcoins with the lowest difficulty to see if I could get some profit from them too.