Serial or vicious murders showing no empathy would  incude:
 
1)Dennis Rader (the BTK Killer) or Bind, Tape, Kill
has his Sun 19Pisces and his Mercury (27PIS) conjunct fixed star Scheat (much pain suffered in his early life)
http://en.wikipedia.org/wiki/Dennis_Rader
 
2)Scott Dyleski (killed visciously, Pam Vitale the lawyer's wife)  he was underage
with Moon in Cancer Mars in Pisces (conjunct Scheat)
http://www.courttv.com/news/horowitz/photo_gallery/index.html
 
3)John Wayne Gacy (the "Killer Clown") who buried dozens of young boys under his crawlspace
   has Pisces Moon at 28 deg. Pisces, AGAIN, conjunct Scheat
   has Sun in Pisces at26 deg.      
http://en.wikipedia.org/wiki/John_Wayne_Gacy                 "              "
 
4)Lyle Menendez (viscious shotgun killing of both parents)in Beverly HIlls  Mars in Pisces
   Eric Menendez   "          "           "             "          "                              Mars in Pisces
both blamed their parents for torturing them
 
5)Timothy McVeigh - young ex soldier from theGulf War says he learned to kill over there
became the Oklahoma City Bomber to avenge the killings of the GulfWar he said
had his Moon in Pisces 18 degrees
http://en.wikipedia.org/wiki/Timothy_McVeigh
 
6) Richard Allen Davis  Triple Cancer (Moon Mercury Venus) killed Polly Klass age 12 after kidnapping her.
http://en.wikipedia.org/wiki/Richard_Allen_Davis
 
this is just a few of them I know of.