Ninkasi Tricerahops is one of my favorite commercial IIPAs and it uses a decent amount of Summit. So does Green Flash Imperial IPA, another favorite of mine. I mainly detect dank resiny tangerine citrus from both of these beers, which use the majority of Summit early on and in the dryhop. For a replacement, Apollo or Columbus would probably be the most similar to Summit.
Some people will tell you that the supposed oniony character only occurs when the grower leaves Summit on the bines for too long. But I believe there is a fallacy in this claim.
Other Summit heavy beers like Devil Dancer taste straight up oniony every year. I wouldn't say that Founders is specifically requesting from the grower that their allotted portion of Summit be left on the bines for longer. Rather, Founders is just using way more Summit and implementing it via a vastly different hop schedule with less complementary hop combos... The same goes for Oskar Blues Gubna. Both of these beers taste oniony, yet all four hoppy ales mentioned in my post focus quite a bit on Summit hops.
My theory is that Summit will yield oniony traits if you overdo it in the 30-5 minute kettle boil range and don't balance it out with fruity hops like Amarillo or Citra. The effects might be magnified if you also incorporate this schedule with a substantial amount of Summit for a long, 10-14 day dryhop.