Origin for City Elf - sell Shianni to Vaughan, don't help Nessa at all, also blame Soris with you at the end.
Ostagar: Kill dog, don't feed this prisoner. Play as selfish, killing loving jerk.
Urn of Sacred Ashes: Desacriface Urn, kill Leliana. Kill Genitivi.
Companions: Slit throat of Zevran. Leave Sten in cage.
Circle: Agree with Cullen and kill every mage (bye bye Wynne).
Brecillian Forrest: Support warewolves and therefore never cure them - let them be mad dogs, make sure lovers won't get along (if you are playing Dalish sleep with one of them), tell widow how Danyla turned into warewolf. Kill halla.
Redcliffe: Leave village to be destroyed. Make Isolde kill Connor (I did it last time, was Allistair mad on me ... o man)
Denerim: Do Ignacio jobs, (if you play Rogue) don't help Slim Couldry at all.
Agree on blood magic ritual to boost yourself in Alienage (kill your own father Cyrion if you are City Elf)
Dlc's: Help Sophia Dryden, allow demon to possess either Amalia or Matthias. Burn down the Amaranthine and kill Architect, also sell Anders to templars.
Orzammar: Help Harrowmont gaining crown, let Branka make new golems, kill Caridin and Shale. Don't recruit Oghren. Kill Ruck after you agreed to lie to his mom. Help Burkel to get his temple, make Zerlinda leave her son on Deep Roads.
Landsmeet: Get Loghain to Wardens, make Anora sole queen, allow her to behead Allistair.
End of game: Make sure Dark Ritual was rejected, and order Loghain to sacrifice himself.
Dragon Age II - be an arrogant mage with praising for Tevinter culture or be afraid of mages pro-slavery bastard.
Intro: Make sure to argue with everybody, show your lack of compassion to both Leandra and Aveline.
Kirkwall arrival: Work for Athenril, be a dick to everyone.
Dlc's: Be ignorant towards Qun to Tallis - make her angry and argue about list, support Janeka to free Corypheus also be a dick to sibling while there.
Act I: Sell mages back to templars, allow Ginnis to take Seamus, tell Ghislain how Ninette was killed with gore details, kick out Keran from templars, don't kill Keldar - give him to judge, kill Idunna, blackmail Thrask about Olivia, sent Feynriel to Circle. Be of little compassion for Anders in his quest. Also brag about pro-slavery to Fenris. Take Carver into Deep Roads without Anders OR if you have Bethany make her Gray Warden. Don't care about Amaranthine conspirators. (If you made Bhelen king) Sell Renvil to Carta Thugs. Leave Sophia Dryden to possess more imbeciles on coast. (if you sided with elves in Origins) Allow Danyla daughter to kill ex-warewolf.
Act II: Support Petrice movement, tranquil Feynriel - when he doesn't want to, kill Javaris, don't kill Gascard, don't care about Hubert, leave guardswoman to herself against raiders, aree with Bella taking Tome of Koslun and then sell Isabella to Arishok, make Varric kill Bartrand with companion of Anders, don't care about Pol in Merrill mission, take money for Athenril from her kid smugglers and leave them to their sad fate. Agree on taking power from Tarohne tomes. Don't care about Keran debt. (If you killed Nathaniel in Awekening) Save Ivan instead of Merin. Kill elven apostates for gold with mercenaries. Tell Viscount to burn qunari bodies.
Act III: Sell Fenris to Denarius, kill Merrill's clan - make sure she will destroy Eluvian, let Varric keep Idol piece from mansion, do everything to estrange Aveline to Donnic, leave Nathaniel in Deep Roads (don't care about quest), make sure Charade will give you gem instead of reunion with Gamlen, gave Orsino people to Meredith instead to fuel her paranoia, agree to help Anders with planting explosives in temple, Emil sent back to Circle, don't do anything regarding Hybris lair, don't kill dragon in Bone Pit, execute Anders and support templars at the end. If you have Circle Bethany then allow Meredith to kill her.
I will add more if I will remind myself more bad decisions to those.