All together and At one fell swoop

All together adverb - Used of a group whose members acted or were acted upon collectively and when `all' and `together' can be separated by other words.

At one fell swoop and all together are semantically related in together topic. In some cases you can use "At one fell swoop" instead an adverb phrase "All together", when it comes to topics like as a group.

All together and at one fell swoop are semantically related in together topic. Sometimes you can use "All together" instead an adverb phrase "At one fell swoop", if it concerns topics such as as a group.