It wasn't really much of Genesect's offensive stats / typing that earned it it's fame, but more of the outstanding coverage it had, plus U-Turn (decent stats / ability should be assumed in upper class OU, since you can't get far with bad stats) For this reason, I think Jirachi is probably the closest you'll get to Scarf Genesect.
Here's another pokemon that could function quite similar to Genesect:
@ Choice Scarf
Timid / 4 HP / 252 SpA / 252 Spe
Trick / Ice Beam / Thunderbolt / Hydro Pump
Though a relatively rarer set, choice scarf Starmie does function in a way quite similar to Genesect- using it's coverage and options to grab momentum as well as target and revenge kill certain threats. Trick is Starmie's 'U-Turn', as it gives you a free switch provided you use it right, and although it does't deal direct damage like U-Turn does it is more of a hassle for bulky pokemon to deal with. Ice Beam and Tbolt are your BoltBeam coverage, hitting thins decently hard despite Starmie's not so outstanding SpA. Hydro Pump is your main click-and-kill move; it's extremely powerful in Rain and is capable of blasting through the defenses of even neutral pokemon. Just like Genesect, Starmie has a bunch of other options, however they are a bit fewer. Rapid Spin is a helpful way to get hazards off the field, and Psyshock can be used as alternate STAB that can hit most poison/fighting types for the OHKO. Thunder and Blizzard can be used in their respective weathers.