Derek Lowe has a good post on some very strong peroxides: http://blogs.sciencemag.org/pipeline/archives/2014/10/10/thi...
Of course quantity matters. But messing about with strong oxidizers is scary. The article doesn't say which organic peroxide it is, and that matters a lot too.
Edit: Given the list of products made at the site[1] (PVC, acrylic paints, etc) it might be MEKP[1]. That's quite a strong explosive.
[1] https://web.archive.org/web/20170830090410/http://www.arkema... [2] https://en.wikipedia.org/wiki/Methyl_ethyl_ketone_peroxide
[1] https://en.wikipedia.org/wiki/PEPCON_disaster#Damage_assessm...
The only organic peroxide I can think of that was ever a legitimate high-power explosive was HMTD, used as a primary in strong detonators, and its chemistry was a bit like swapping peroxide for the nitro in RDX (the explosive used in C4 plastic explosives).
I suspect this site has a LOT more material than that.
Nuclear bombs don't have a monopoly on large explosions - their claim to fame is how light the bomb can be, not how large the explosion.
I get what you mean in relation to the Hiroshima bomb, but they do have a monopoly at some value of "large". All of the bombs exploded in WWII added up to about a 3 megaton TNT equivalent. There have been single thermonuclear weapons with roughly 10x that amount or more.