feel pain.....
Each hp they take, thow a thumbtack at them.
lol
seriously....
1) take the kid gloves off. the players aren't your children. the game thrives on survival.
2) think of Dark Sun, if you ever ran it, it was merciless. Do the same.
3) Make your villians ruthless. if they are murderers, make sure they have hostages and are NOT afraid to kill them.
4) make 1 encounter that will trounce them if they don't parlay. don't kill them, just humiliate them. IE trounced and hung up on trees as an example for those who dare to come after El Badboy. Heck, cut off an arm, or a leg, or some other misc body part.
suggestions on low level creatures with high success rate.
1) giant ants and normal ants and a whole lot of broken jars of honey over sleeping pcs, most likely delivered by quicklings.
2) glue/tanglefoot essense the swords to their sheaths, loosen bow strings or damage them deliberately.
3) get 10 level 1 sorcerers or wizzies. They are trying to join a guild and in order to do so, they have to prove to the guild that they can work together. The harder the target, the better the chance of winning the guild's approval.