Ndtyhij

I'm a really really new player. Is it good etiquette for a DM to get upset that you're killing or beating their encounter?

A guy said he would DM for us in a one-shot. Before we ever started he kept saying and laughing how we are all going to die. Then we actually beat the first encounter and he was visibly upset (we wasn't supposed to).

So he had 2 beholders come flying at us before we could get our heads together and started another encounter after that, because we won AGAIN barely.

He said we got teleported to an enclosed cave full of gold and a black dragon was waiting for us. I actually 1 shotted the dragon with a quivering palm. He says"and out of no where another black dragon flies in" - it was an enclosed cave.

After a few turns our paladin wins with geas and commands it to sleep for 30 days.
Then a third one comes in. It was getting too ridiculous and to be honest was not fun after I realized that he didn't plan ANYTHING after the first encounter because he was supposed to kill us and literally just made up everything after the first encounter.

Is this what I should expect from all DMs?

No, quite the contrary. The introduction of the Dungeon Master's Guide contains some relevant guidance.

You're the DM, and you are in charge of the game. That said, your
goal isn't to slaughter the adventurers but to create a campaign world
that revolves around their actions and decisions, and to keep your
players coming back for more! If you're lucky, the events of your
campaign will echo in the memories of your players long after the
final game session is concluded.

and further down:

The success of a D&D game hinges on your [the DM's] ability to
entertain the other players at the game table. Whereas their role is
to create characters (the protagonists of the campaign), breathe life
into them, and help steer the campaign through their characters'
actions, your role is to keep the players (and yourself) interested
and immersed in the world you've created, and to let their characters
do awesome things.

If a DM is running the game in such a way that takes away the players' fun, s/he is doing it wrong. Taunting the players, becoming upset when they succeed, and throwing out continuous obstacles intended to turn successes into failures certainly fall under that category to me. You said it yourself, "It was getting too ridiculous and to be honest was not fun..."

To answer your last question first:

Is this what I should expect from all DMs?

No, this is not what you should expect. To be honest, if this was typical behavior, it's pretty unlikely that people would still play Dungeons and Dragons. There was a time when it was pretty common to have an antagonistic style between DM and players - Gary Gygax, for example, was famous for this kind of style; however, his encounters were intended to be solvable, just very hard to solve.

That said, that style of play definitely is the minority now. I'm sorry that this was your first experience with my favorite hobby, and I hope that it hasn't ruined it for you.

If you're still interested, I'd recommend looking for a local hobby shop that runs D&D Adventurers League, as I've had good experiences with that program. Pathfinder Society is another organized play league you might be interested in as well.

As suggested by commmenters, I'd highly recommend checking out Critical Role for an idea of what a more typical session would be like.

No, a DM is not meant to be adversarial to the players. It says so both in the Lost Mines of Phandelver adventure booklet (from the 5e Starter Set), and in the official Dungeon Master's Guide:

You’re the DM, and you are in charge of the game. That said, your goal isn’t to slaughter the adventurers but to create a campaign world that revolves around their actions and decisions, and to keep your players coming back for more! (DMG, p. 4)

That being said some groups may enjoy a challenge where the DM plays a harsh game. But that is something that must be agreed upon by everyone beforehand. In my experience (limited to my own Dungeon Mastering and the several podcasts I listen to), DMing is about creating interesting and immersive stories for your group.

The DM's role depends on the style of game they're playing.

D&D is a system for playing games about exploring dungeons and fighting monsters. The DM's job is to keep the game moving, maintain some coherent ruleset, and try to manage an enjoyable game for the participants.

Beyond that, most other factors of the resulting gameplay will vary by the players, the DM, and the type of game they want to play.

There is no single "right" way to play D&D. People approach the system with their own preconceptions, often based on memes and cultural portrayals of tabletop RPGs. They may have different assumptions about the DM's role and authority. And when the DM and players are out-of-sync about their expectations, problems occur.

For example, if the group wants to use D&D to play a story-like adventure, the DM may act in favor of the PCs (player characters), using in-game challenges to advance the narrative and give the PCs opportunities to shine. Or, the group could agree to a "DM vs. PCs" structure, in which the DM competes against the players by trying to defeat their characters with traps and monsters. Either approach is technically valid; however, the game runs more smoothly when the players and DM agree on their expectations in advance.

Ultimately, it's the DM's responsibility to move the game along in a way that the group has fun. Just remember that "fun" means different types of gameplay for different people, so it's best to discuss in advance what type of gameplay to expect.