Without knowing more about why you think your scene is going to be an anticlimax, it's kind of difficult to offer any particular advice.
Anticlimaxes are disappointing more or less by definition. They typically come about when your story fails to deliver on the expectations you've set up, especially when the audience gets the impression that the author is taking the easy way out or doing something "cheap." For example, if you've built up an intriguing, intricate, and puzzling plot, and people are looking forward to how you're going to tie everything together and resolve all the mysteries you've set up, then they're going to feel it's an anticlimax when you finish off with, "And then they all woke up and realized it had just been a dream! The end!"
Likewise, if there's this really cool villain-guy who's been lurking around in the shadows, and you've been building up to having her finally meet the heroes and have what the audience assumes will be a really great showdown, then the heroes end up roflstomping her with almost no effort with their super-weapon or whatever, that's anticlimactic. Or, conversely, if you've been setting up the villain as this nigh-invincible mastermind and have the audience wondering how the heroes are ever going to manage to defeat her, then have them come up with some weird and unsatisfying trick that makes the showdown incredibly one-sided, that's also anticlimactic. Like, if it turns out the villain is totally awesome in every way except has a crippling fear of the color blue, so to defeat her the heroes end up painting themselves blue and reducing her to a crying wreck, readers might find it funny, but they'll probably also feel gypped.
It can be tricky to avoid anticlimaxes, because they require being very aware of how your audience is responding to your work and what their expectations are. For example, you may not realize that people are getting entirely the wrong impression from your writing, and this character you'd intended to only be a minor bump in the road is coming across as a major villain to the audience, who are really sure this person is supposed to be important and impressive and get annoyed when they're not. Or you have this really intricate plot going on that hinges on something seemingly innocuous that you planted a long time ago, and you've been trying to plant hints as to what's really going on all along, but when you reveal it people just didn't pick up on it and are all, "Whaaaat? That's stupid!"
So, it can be hard. To avoid anticlimaxes, you have to be very careful about painting yourself into corners. If you've set up this impregnable fortress that the heroes somehow have to infiltrate, then find yourself going, "...well ****, how on earth are they going to pull this off??", you're in trouble. That's when authors get tempted to just invent something hurriedly, regardless of how much sense it makes. If you've put yourself in that situation, you just really need to allow yourself time to think and come up with a good, plausible plan; don't feel pressured to go with the first crazy scheme that pops into your head. If you're writing/planning far enough out ahead of your posting, you can also go back and tone things down earlier on to give yourself an easier time of it. With those sorts of situations, you ideally want to start out with the solution you're going to use for the story, then frame the problem such that it flows naturally from the setup.
Also, you're always possessed of the most important tool you have while writing, which is directing the reader's attention. A good rule of thumb is that the more time you spend setting something up, drawing people's attention to it, and so on, the more effort readers expect it to take to resolve. If you've spent pages on how terrifying this trainer is in battle, readers are going to be disappointed if the hero is able to defeat that character swiftly and easily. If you laud up this puzzle as nearly unsolvable and difficult even for a genius, then your character glances at it for a couple of seconds and solves it in under a paragraph, again your readers will probably cry foul. Make the effort fit the reward. So, if you intend for something to have a snappy, simple solution, make sure you haven't been shining too much attention on it and thus signaling to the audience that they should be prepared for something big.
