Subject/object in this sentence: "Against no one was feeling more bitter than against Rhett Butler"

It's easier to understand in context (emphasis and comments are mine):

It was a situation made to order for speculators and profiteers, and men were not lacking to take advantage of it. As food and clothing grew scarcer and prices rose higher and higher, the public outcry against the speculators grew louder and more venomous. In those early days of 1864, no newspaper could be opened that did not carry scathing editorials denouncing the speculators as vultures and bloodsucking leeches and calling upon the government to put them down with a hard hand. The government did its best, but the efforts came to nothing, for the government was harried by many things.

Against no one was [this] feeling more bitter than against Rhett Butler. He had sold his boats when blockading grew too hazardous, and he was now openly engaged in food speculation.

With some context it's a bit easier to make sense of the original example:

The public outcry against the speculators grew louder and more venomous.[...] Against no one was feeling more bitter than against Rhett Butler.

The subject of the bolded clause is the noun phrase feeling which refers to the public sentiment. The structure of the sentence is complicated by the fronting of the negative adjunct (read 'adverbial') Against no-one.

Because this negative adjunct has the effect of negating the whole sentence, it causes compulsory subject-auxiliary inversion. For this reason we see the Subject feeling occurring after the verb was instead of before it:

• Against no one was feeling more bitter than against Rhett Butler.

We can compare this with the ungrammatical example below:

• *Against no one feeling was more bitter than against Rhett Butler.

Of course, because the noun feeling has an -ing ending, it's occurrence after the verb was makes it look a bit like it's part of a past continuous construction, and this makes the sentence a bit more difficult to intuitively analyse.