Just a summary of this entire thread. Might be wrong, feel free to correct the list or top-up new bad developers into the list to help more ppl to be informed.
Due diligence to research around the internet is being responsible for our money.
It's not small money buying small stuff at pasar, it's real big money earn over years with our own blood & sweat.

Hope this helps.

Super Bad developers
Villamas
MKland
IOI Properties
Winfast
LBS
Titijaya
Aset Kayamas
MKH
WCT
Numestro
Glomac
Mayland
Avaland (MCT)
Land & General Berhad
Suntrack
TALAM (Trinity Cooperation)
Masteron
Pinnacle
Choon Tian Real Estate Developer Malaysia
BHL
Mammoth
Monoland
Magna Prima

Below Average developer
Malton
Tropicana
Berjaya
Mahsing
Binastra
UOA
Ecoworld
Exsim
IJM Land

Ok quite good
Skyworld
PV
SP Setia
Sunway
Sime Darby
IGB Corp
UEM
I&P
Gamuda
Bandar Utama
Al Batha Bukit Kiara
Bandar Raya Development Bhd
Eastern & Oriental
BRDB
Tan & Tan
See Hoy Chan
Zalam
Econpile
OSK
Guocoland

Surprising no one discussing Akisama?

Chin Hin where?

What made you think that UmLand as Wow?

What about Metrogen - the developer of condominiums such as X2 and Tasik Residency in Puchong?

actually what are the criteria to differentiate developer good/bad? Or just general reputation of the developers only?