This matchup is similar to the Lucas vs Pit matchup in some ways, but here's how it goes.
Both Ness and Pit do have some poor Melee range. Pit's longer ranged melee moves are F-tilt and F-air, and both dont come out as quickly as Pit's other moves. There isnt much to talk about this part.
Note: Like Lucas, Ness' Fsmash is a reflector when Ness swings his bat. It can be used against Pit's arrows.
Ness is kinda small and is somewhat hard for Pit to hit, but not as small as Lucas though.
Ness' F-air is useful in the fight, since Pit lacks range, and F-air has good priority, and duration time, comes out fast, with a small amount of lag. B-air has less lag and more spammable, as well as it's sweetspot being a kill move.
Ness' PK fire, like Lucas', isn't completely recommended in this matchup. Ness lacks the PK fire ATs that Lucas has, but Ness' PK fire does hit multiple times. This could somehow be used to eat Pit's jumps up, or stop him long enough to grab him or hit him, if the Pit doesn't escape quickly. Remember that Pit has reflectors, so it's tempting to use.
PK Flash isn't really useful against a Pit, considering the Reflectors he has, and that Pit can shoot an arrow at you while you're doing it, so Pit can shoot you from long range, or punish you if he's close enough. Like Lucas' PK Freeze, if reflected by Pit, it could hurt Ness if he's in the blast radius (Like that's ever goin to happen in a match).
PK Thunder is very threatening to Pit in some cases. Remember that Pit's reflectors can only protect him from what's coming at him from the front, so control the PKT so that it goes behind Pit's Mirror Shield, and hit him. As for Angel Ring, it's harder since it's reflecting range is larger than the Mirror Shield's.
PKT can be used to take down Pit's recovery. Use it against his Up-B and neutralize Pit's recovery. But remember, when you first knock down a Pit, the Pit can choose to glide, use a reflector, or shoot arrows as he is recovering. More about PKT will be discussed later.
PSI Magnet is simply to counter Pit's arrows, and gain some health from it, nothing special. Note that when the move stops, it has a little windpush effect, that part isnt really useful. You can use it to stall in the air, sort of like Fox can with his Reflector, just not as long, and repel Pit's arrows that way.
Pit has some problems with F-air's range, and also can be used to stop him from recovering. You can choose to spike him with D-air if you wish, but just be careful of Pit's U-air. PKT is a good choice against his Up-B recovery, as mentioned before.
B-throw hurts Pit so much, usually KOed at around 110%, depending on where you are and the DI Pit makes, poor angel
B-air is also a kill move when sweetspotted, but you better measure the distance from Pit if you want to land it.
I really dont know how Ness usually applies D-smash or U-smash, aka, the Yo-yo, since it's rarely used. It does not outprioritize Pit's Rapid A, or Angel Ring.
Now, Pit can do a lot of things to annoy Ness, despite the PSI Magnet against his Arrow thing.
IMPORTANT! Here's the big thing that all Ness players must know when against a Pit.
Because Ness has less Recovering options than Lucas, especially without such ATs like Zap jump, or tether recovery, Pit can take down Ness easier than he can take down Lucas when Ness is trying to recover. Here's what a Pit can do against Ness' limited recovery:
1: Shoot an arrow at Ness to disrupt him, which forces Ness to use PKT again, or to eat up Ness' Mid-air jump.
2: Mirror Shield Ness' PTK Recovery, after Ness hits himself with PKT that is, to "Reverse" him and KO him. Note that Pit has to time it right or the Pit will get punished.
3: Pursue Ness with one of his aerials, but many Pits would rather not risk getting hit by the PK blast. If Ness isnt using PKT at the time, most Pits would use either F-air or U-air, or B-air for the kill.
4: Fly over Ness to take the PKT hit and negate PKT as well as KOing Ness.
5: Shoot an arrow at the PKT therefore destroying the PKT, negating Ness from Recovering, and KOing Ness. This is a lot safer than Number 4.
6: Edgehog. Pit's Up-B, when used next to the ledge, while airborne (used mostly when Pit is trying to recover), can help Pit grab the ledge quickly.
7: Use Up-B near Ness to "Wingpush" Ness and it screws the Ness up when trying to angle his PKT. The "WingPush" can destroy Ness' PKT as well when in range, and that means bye bye Ness.
Note: Like Lucas, Ness is one of the characters that can get D-tilt spiked by Pit while hanging on the ledge.
Pit's D-tilt spike works when the opponent is at Pit's feet when Pit is crouching. Of course, the opponent cannot be on the ground. Pit's D-tilt spike is quite strong, for a move that does 11% damage.
Ness' Advantages
-Somewhat small and is hard for Pit to hit
-PKT and F-air messes up Pit badly when Pit is trying to recover
-Pit is very vulnerable to PKT when using Up-B to recover
-PK Fire, when used correctly, can be used to eat up Pit's Mid-air jumps
-PSI Magnet can be used against Pit's arrows
Pit's Advantages
-Pit has reflectors that help lessen Ness' projectile usefulness
-Pit can punish Ness when he uses a move that makes him Vulnerable, like PK Flash and PKT. He can use Arrows to punish him at a far distance, or a different attack when Pit is close and when Ness misses.
-Pit's Edgeguarding, Ledgecamping, and Gimping capabilities are Exceptional
-Pit is very good at Shield Pressure. Rapid A, Angel Ring, and N-air are the primary Shield-pressuring Moves that Pit has. U-air is also another
-Pit has so many options to stop Ness' limited recovery. He can even stop his recovery with Arrows (especially the PKT), a safe distance from harm.
I'd say this matchup is at about 55-45 or 60-40 in Pit's favor, main reason is because Ness is screwed when trying to recover in this matchup against Pit. What do you think?