I'm thinking all those mini-series/graphic novels by Starlin which the majority were released as OHC's:
Thanos: The Infinity Revelation (2014) OGN
Thanos: A God Up There Listening (2014) #1-6
Thanos Annual #1 (2014)
Thanos vs. Hulk (2014) #1-4
Thanos: The Infinity Relativity (2015) OGN
The Infinity Entity (2016) #1-4
Thanos: The Infinity Finale (2016) OGN
Thanos: The Infinity Siblings (2018) OGN
Thanos: The Infinity Conflict (2018) OGN
Thanos: The Infinity Ending (2019) OGN
It might clock in at around 1000+ pages.