As a DM, do you hate it your monster whiffs its attacks, and now it feels less of a "big threat" and more just "amusingly inept"?
Here's some advice to make all characters (dungeon master NPCs and player PCs) feel more competent with only a minor change to how you describe combat roll outcomes.
Here's a stereotypical scenario:
DM: "The giant attacks twice with his club!" Rolls a 2 and a 3. "Two misses."
The perceived result, the giant has failed twice, the giant is slow, clumsy, and/or incompetent.
We can do better.
Here's an alternative description of same scenario:
DM: "The giant attacks twice with his club!" Rolls a 2 and a 3. "You block the first blow with your shield, and quickly sidestep the second!"
The perceived result, the player's prowess and dexterity saved them from the giant's attacks.
The point here isn't how colourful or expressive the outcome is described. You can (and I encourage you try) to add more flavour... but that isn't the point of our examples, and outside the scope of this quick discussion.
The point is what is being described. The first was the missed attack, the second was the successful defence.
The advice is, on roll results, describe the successful number. If the attack hits, describe the character's attack. If the attack fails, describe how the other character defended themselves.
All characters and players will immediately feel much more competent.
Another stereotypical example:
Character attacks with sword, rolls an 8. "Miss."
Opponent attacks with sword, rolls a 9. "Miss."
Perceived result, two people flailing at each other ineffectually.
Alternative to the same:
Character attacks with sword, rolls an 8. "Parried!"
Opponent attacks with sword, rolls a 9. "Dodged!"
Perceived result, two people fending each other off, each holding their own against the other.
Its easier if you think of the target number (the AC or DC) as an "active participant" in the result. Then it becomes less about one number failing to reach a result, and becomes about one number overcoming another.
This is a quick thought I had and originally posted to Twitter. I'm certain similar advice has come up before, but my searching is failing me. If you know of similar threads/posts along this lines, please share it with me, as I'd like to read up more on the topic!