They won't be making that mistake again
Well they already did...though not as generous. While that one was worth 2.85 million I have run on several promos since earning 100-300K each time. Plus many smaller runs. Well is dry at present though. Amex is unfortunately mainly do cash-back offers at present. And while the cash is nice, it is not as nice as hundreds of thousands of points.
However OP was asking about sign on bonii. Too many to list them all but some include:
The recent ANZ one was worth 250K for $0 for my wife and I (though with qualifying spend.)
They had one years back which 37.5 K for $0. Took out and applied for wife and I, and then re-applied = 150k for $0.
Amex did have 80K bonus on the Platinum Card when the perks were better than it currently is by a goodly margin. Did cost $450, but with a free flight worth $500+, genuine travel insurance that each card holder gained without any spend including on it the travel, including supplementary card holders s that wife and daughter could travel separately with free travel insurance and other good perks (So worth $500-600 per person per year). Referred the wife to gain another 20+80K as well.
Citibank have had a steady stream over the years. Jetstar not long back. 16K there, 20K here, 40 K there, 50K here...they all add up. Even better when they are not QFF points.
There have many been others for free or low amounts. One/s that have a significant fees I usually tend to avoid. However sometimes the banks would refund card fees on cancelling.
Sign-ons and promos come and go in waves. Sometimes there will be a drought. But the drought always breaks.
Currently there is a steady stream of sign-on bonii, and cash-back promos, but bonus points for spend are on the lean side.
Common point with all of them though is Carpe Diem. Spend bonus points are the most lucrative for me though, and so hopefully the drought on these will break soon.