His jab would unique. I don't believe other smash characters have too much variance in their jabs - I know with Falcon you can do an alternate combo with a different timing - so with his jab I'd let him do several of his staple combos from DMC3/4 with consecutive A presses of different times/pausing in between some presses. (Don't know too much about Bayonetta, but apparently she only as one additional jab combo).
Forward-tilt - easily would be his standard swordmaster attack, spins his sword in front of him. Multi-hits to end a damage-combo as opposed to a kill-combo.
Up-tilt would be high time, an sword uppercut that lifts opponents for combos. Like in DMC, holding it will make Dante go up with the enemy, making follow-ups easier.
Down-tilt - While for simplicity's sake I imagine most of Dante's moves being carried out by his sword Rebellion (but there'd be room for other weapons with Custom Moves), I'll throw in a reference to Beowulf for his d-tilt. Just a sliding kick, similar to Cloud.
Neutral-air - Aeriel Rave, sword slashes which suspend him in mid-air.
Forward-air - Helm-breaker, falls down forward with his sword (like the falling part of Ike and Cloud's Up-B)
Down-air - Spins around upside-down while firing his guns. From DMC2 which is a pretty bad game, but that move did look cool, and it'd be a somewhat unique down-air.
Up-air - Upwards spinning attack with Cerberus, the ice-nunchucks. A bit unsure about this one, but again, I think it'd look cool.
Back-air - Shoots his guns behind him, inspired by his Gunslinger style.
Dash-attack - Stinger, plunging forward with his sword, and if you mash A while you do it, it transitions to Million-hit stab, a multi-hit stabbing move.
His smash attacks I'm not too sure about. Maybe they'd be carried out by Sparda, from the original DMC. Those attacks extended out and packed more of a punch than any other weapon in that game.
Neutral B - gunshots. Side-B - Trickster, essentially teleport left or right, for recovering and general movement. Down-B - Devil trigger, makes you stronger for a while and is charged similarly to Cloud's limit I guess. Up-B - idk, some sort of sword leap.
Maybe give him a grapple recovery based off his DmC grapples as well. Small shoutout to that game.
Costumes: his popular young Dante look from DMC3 would be his main design, then I guess his costume from DMC since it's had a couple of appearances. Not sure. Palette swaps that reference the other games if there isn't enough development time/desire for proper models.
These are mostly of the top of my head and I'd easily change a lot of this with more thought, but yeah, you could do a lot with Dante.