I've been in a campaign for the past 4 months with a very controlling DM and a player who has been dubbed their favorite.
The DM in question is very flexible with anything in their game... as long as it benefits their favorite. Since I don't want to use their real name, I'll call her Hannah.
We are currently level 6 in D&D 5e and Hannah has obtained a sword with 4d6+2d4 damage with every strike, while the second most damaging weapon goes to my player with a total of 2d6 damage. Every game session they add more damage dice onto their sword.
The DM has backed this up and is the one who caused their weapon to grow more powerful for no reason other than they said so. This makes fights less enjoyable because Hannah kills every opponent in 2 strikes and leaves the rest of the players annoyed and bummed out.
Hannah also has a way to silence players that she doesn't approve of. Her character has a bunch of tranquilizer darts and, when it hits another player's character, will silence a player for 15 minutes of talking in real-time. She does this sporadically and refuses to let plans be anything but ones she 100% approves of. Quite a lot of these ideas nearly caused multiple TPKs which has made everyone but her go through 2 other characters in the campaign.
The rest of the party has been trying to plan to kill Hannah's character and I'm pretty sure that it's going to make the situation worse if it happens. Hannah really does love her character and I don't want to get rid of her, I just want to fix the situation so there's no more favoritism.
I realized that leaving things out about the dynamic of the rest of the party puts Hannah in a light that makes her seem like she's being mean for the sake of annoying the rest of the party but that's not really true.
The logic behind the Tranquilizer darts is that she got normal darts at the beginning of the game and later filled them with Sleeping Draught. She's a Lawful Good and likes to talk things out while the rest of the party is a bunch of murder hobos. This clash of alignments makes Hannah's voice not heard as much since her morals don't commonly align with the rest of the party. If a player has an idea that she 100% is fully against, she tranqs them. the most recent silencing was when the rest of the party was planning to seduce and then kill the King's Lord of Finances in order to get money and learn the Kingdom's secrets. The Character of the player is then unconscious and unable to do anything and the DM won't let the player have a say in planning for 15 min. Her views make our ideas clash and if she removes the person who's making the most outrageous idea, the playing field is more even for her.
She isn't tranqing every player left and right. She mostly feels left out because her ideas are usually vetoed. And in the end, we usually incorporate some of her plans into the overall goal. (We didn't kill the Lord of Finances, we locked him in his own dungeon and interrogated him instead.)
She is a friend of the DM whilst the rest of the party are acquaintances, this closer connection makes the DM sympathize with her more. Most of the party is female, including myself and the DM. If an argument springs up about how Hannah is ruining the party it's going to turn into a yelling match extremely fast. I really hate conflict so I've been trying my best to avoid arguments as much as possible. I hope that this helps with your advice on how to stop this from happening.
How do I tell the DM and Hannah that the favoritism and refusal for other players' ideas is making the campaign close to unbearable? And how can we fix the favoritism issue so everyone is treated fairly and equally?