We can get a list of the ordinals at: archive.org/details/bitcoin-ordinal-inscriptions.csv and then sort them by payload size with:
sort -k6 -n -t, ordinals.csv -o ordinals-sort-size.csv
This shows to us that as of block ~831k, there are 4 ordinals which are far far larger than any other between 3 MiB and 4 MiB, at about 10x larger than then 5th one d115a6e689086fd587e5032f24ba2a8c01f2f87cba758c9d5eb8cf7f6e9a816a
In those cases, a single inscription takes almost the entire block, and the inscribers must have had direct dealings with their mining pool:
- ordinals.com/inscription/4af9047d8b4b6ffffaa5c74ee36d0506a6741ba6fc6b39fe20e4e08df799cf99i0: 3,946,469 bytes (image/jpeg). Bitcoin Magazine cover showing the face of Julian Assange. tx 4af9047d8b4b6ffffaa5c74ee36d0506a6741ba6fc6b39fe20e4e08df799cf99 block 786501 (2023-04-22). Mined by Terra Pool.
- ordinals.com/inscription/0301e0480b374b32851a9462db29dc19fe830a7f7d7a88b81612b9d42099c0aei0: 3,915,537 bytes (image/jpeg). Taproot Wizards ad. This was apparently the largest block ever mined at the time: www.reddit.com/r/Bitcoin/comments/10r6t1l/the_first_4_mb_block_in_bitcoin_history_mined_by/ and received some notice. tx 0301e0480b374b32851a9462db29dc19fe830a7f7d7a88b81612b9d42099c0ae block 774628 (2023-02-01). Mined by Luxor pool.
- ordinals.com/inscription/79b91e594c03c8f06d70c44a288a88a413c540abca007829ca119686a7f979dai0: 3,878,842 bytes (image/webp). "Bitcoin War Bonds". A spoof of something. No time to understand now. tx 79b91e594c03c8f06d70c44a288a88a413c540abca007829ca119686a7f979da block 777945 (2023-02-23). Mined by Terra Pool.
- ordinals.com/inscription/b5a7e05f28d00e4a791759ad7b6bd6799d856693293ceeaad9b0bb93c8851f7fi0: 3,379,682 bytes (video/mp4). Short looping video of a "purple frog drinking from a glass with a straw". Yes you heard that right. TODO context? tx b5a7e05f28d00e4a791759ad7b6bd6799d856693293ceeaad9b0bb93c8851f7f block 776884 (2023-02-16 ) Despite being huge, this received very little attention, the only Google mention is at An overview of recent non-standard Bitcoin transactions by 0xB10C. Mined by Terra Pool.
As of 2024, all of the big ones were made in early 2023, so it seems that the trend has died down a bit.