AIG wasn't a bad, but an insurance company that failed because it took on too much risk. If, for example, AIG was that only one to fail I'm not sure it would have taken down the economy with it. I see them as someone that got embroiled in the "sub-prime mortgage crisis", but not necessarily a perpetrator (unless I'm missing something).
AIG wasn't a bank but it was insuring a lot of the bank's assets, including securitized mortgages. By taking that risk off the banks' balance sheets, they let the banks take on more risk than they otherwise could have. So maybe AIG wasn't a perpetrator, but it was an enabler.
