Why does it add "v'Gam Avru Brisi"?
Radak #1: Do not say that "Chata", i.e. Shogeg. They also transgressed My Bris at Har Sinai to do all that I will command them. I commanded via Moshe "Elav Tishma'un" (Devarim 18:15), to obey prophets, and they transgressed your word!
Radak #2: The five "Gam"s in the verse hint that [Achan] transgressed the five Chumashim.
Malbim: The sin was double. It included Chilul Shabbos; they conquered the city on Shabbos, and [Achan] took from Reshus ha'Rabim to Reshus ha'Yachid. Shabbos is "Bris Olam" (Shemos 31:16).
Why does it add "v'Gam Lakchu Min ha'Cherem"?
Radak #1: Every "Gam" includes. Even had Yehoshua commanded without a Cherem, they would transgress the Bris (refer to 7:11:1:1), and now they also transgressed a Cherem!
Refer to 7:11:1:2.
Malbim: In addition to Shabbos, they transgressed the Cherem.
Why does it add "v'Gam Ganvu"?
Radak: Had they taken openly, it would not be so bad. They stole covertly, as if they intended to hide from the Creator!
Why does it add "v'Gam Kichashu"?
Radak #1: Perhaps someone sensed [that Achan took], and Achan denied it.
Radak #2: In the end, Achan denied, until Yehoshua told him "Sim Na Chavod la'Shem" (verse 19).
Refer to 7:11:1:2.
Malbim: Via stealing covertly, they deny Hashgachah, and act is if Hashem's eye does not see.
Why does it add "v'Gam Samu vi'Chleihem"?
Radak: This was to deny more
