It sounds like you're afraid of the MC killing everyone off! I have to ask: have you played? I think I can at least allay some of your fears in that area.
I am only talking about Apocalypse World here, by the way; other games are other games, and different things may be true.
1) I mean, at the end of the day, it sounds like you know that the issue is one of trust in your MC. And it sounds like you don't think you have MCs around that you can trust. Which kind of sounds more like a playgroup issue than an issue with the game! It may not be the game for your group, and that's cool. But I wonder: in my experience, people are generally pretty surprising. And in RPGs, people usually want the other people around them to have fun (otherwise stop playing with those people, jeez). Generally, when I see people new to AW-style games run them for the first time, they are scared of being a 'killer GM' (the rules make it sound super easy to kill PCs!), and pull their punches way more than they need to.
2) "You land on a bear"--what exactly is wrong here? Presumably the roll this player is making is "act under fire"--which means that, if the player is rolling, then the situation has already been established as dangerous (otherwise no roll necessary!). If it had been established prior to the roll that bears were at the bottom of the wall (maybe the bears are the fire), then, well, sounds like you knew the risks going into it, and "deal harm as established" is a valid MC move to choose. If the bear is being introduced wholecloth by the MC at the moment of failure, then, presumably, the GM move being applied is "put them in a spot". And in this situation, note that it is not kosher for the MC to introduce a bear AND have it deal harm before giving the PC a chance to react. Instead, introducing the bear allows the PC a chance to attempt another move--and AW PCs tend to have plenty of ways to deal with a bear in one roll.
3) It's way harder than you think to kill a PC. The MC is waaaaay less powerful than the PCs in Apocalypse World. By which I mean: in practice, the players control what happens. Really. As an MC, most of the time you're only making hard moves when the players roll poorly, which the players do less than half the time usually. And you have to do multiple hard moves to set up doing harm at all. Gotta establish the harm, then deal it. And even once you do the harm, IF it's enough harm to kill the PC, they can take a debility to not die anyhow.
4) In which I actually get down to answering your question! Here's what I like about Apocalypse World. I come from a trad games background (mostly AD&D into 3.0/5 into 4, with some White Wolf thrown in, typical stuff). Apocalypse World was the game that taught my play group to trust each other--it's hard to describe the feeling but you might get it. For the first time, two things were true about our game experience that had never both been true before. Firstly, everyone sitting at the table was on the same side. We were all playing, not to beat each other, but with the primary goal of discovering what this world was and who our characters were within it. And secondly, nobody at the table had any idea what was going to happen next. I was the MC, and I'd always thought of myself as a good GM, I knew not to (obviously) railroad, and I knew how to pull my punches to keep things balanced but not easy. But with Apocalypse World, I'd get to the end of a session and be like, "holy shit, I had *no idea* ANY of that was going to happen". It kind of made me realize how much I'd actually been (somewhat unintentionally) railroading the whole time in other games, in contrast. I was also mentally exhausted at the end of those first few sessions in a way I, as an experienced GM, was not used to feeling! But I got in shape eventually, and the game was life-changing, and I'm not using that term hyperbolically.
5) So yeah, trust is hard, especially if you're not used to it in the context of RPGs. But do you trust your players/MC to at least play by the rules as written? I'm sure you have a rules lawyer or two in your group. The rules keep the MC in check, hardcore.
Does any of this make sense? Do you kind of get where I'm coming from? I'm happy to expand on things.