A warlock 1/rogue 2 can do decently.
Hit with booming blade and disengage.
2d8+2d6+3 = 19 *0.5 = 9.5 DPR. (move)
1d8+2d6+3 = 14.5 *0.5 = 7.25 (don't move)
In fact, it's probably the highest damage possible at level 3.
It increases at level 5 to
4d8+2d6+3 = 28 * 0.5 = 14 (moves)
2d8+2d6+3 = 19 * 0.5 = 9.5 (don't move)
Which isn't too much behind a 2-handed fighter. (at 6, with 20 Str).
4d6+8 = 22 * .6 = 13.2 (+ action surge, precision strike).
Then it really takes off at level 9.
It also comes with the other walock goodies. Including 5 invocations (at-will disguise self). Though I'm really torn between chain (invisible familiar fits so well with invisible master) and tome...
You don't even need to be a warlock.
Variant Human lvl 3 Rogue Swashbuckler - bonus feat is Magic Initiate (Warlock) - Booming Blade as one of your cantrips, plus Hex as your 1st level spell.
1d8+2d6 (sneak)+1d6(Hex) (doesn't move)
1d8+2d6 (sneak)+1d6 (Hex) +1d8 thunder (moves).
As you level up you increase both sneak attack and cantrip damage.
Although in the long run, taking Magic Initate (Wizard) and going Booming Blade and Find Familiar may net you more damage, simply because an owl can give you advantage on your one attack a round, making your attacks land more often.