There are less options for being bad than for being good, but it is
possible. The fastest way to experience a bad reputation without
actually doing anything bad is to seek sanctuary in a church. I
recommend this for anyone. There is a whole range of game and story
options that only take place after seeking sanctuary and/or taking a
trip to jail. You might want to save your game first though :)

Attacking the town guards is another sure path to evil, and blowing up
the town inn with failed alchemy experiments is not really evil but it
does seem to affect your local reputation. Plus you can break into many
of the merchants at night, sneak into and out of towns, annoy the guards
at city hall and much more.

Have fun on the dark side!

DC