It really depends on how well established the fund is.
LPs are really looking for 20%+ IRR to make the hyper-illiquid, long-term risk worthwhile. Maybe really more than that if they are being honest. Given that venture is the most illiquid, earliest-stage category of all, 25% IRR really probably is necessary to honestly make it worth it.
Insane funds can do much better, 50-70% or higher IRR.
And the best tiny funds can do better, just because of the law of smaller absolute numbers in venture.
But backing it into multiples, at the end of the day, if you have an established brand as a VC firm that LP want to stay with — 2x net of fees is good enough to get another fund. LPs want 3x net or more, but 2x net is “good enough” to re-up. And even, you can do less if it looks like your last 1-2 funds are getting to >=2x net but not there yet.
That can back into as low as a low-teens IRR, depending on entry time / time horizons.