how large traffic can ddos shield defend? 500Gbps offen occurs in games industry.

I think specific numbers are hard because of the varying types of DDoS attacks and nuance in how they are conducted. Vendors are hesitant to make very specific promises about those numbers.

The real answer is that average DDoS attacks are still far lower than 500 Gbps. (Google search "average size of DDoS attack" and comb through several recent reports and analysis). I've seen 150 Mbps to 5 Gbps reported as an average size.

A 2.3 Tbps attack was reportedly mitigated by shield.. You can find reports about this on several news sites.

I can't find any official numbers or limits in AWS Shield documentation. Again, likely because of nuance in how these attacks are conducted and customer's specific configurations.