See Peculiar Distortion.

OK, making a peculiar overpowered pie-busting card out of Path to Exile is a little redundant :) But I still feel like path is closer to white's colour pie than Unmake is, even though I love Unmake as a clean design.

This one feels a bit on the nose to me. Everything's kosher, but...

As Jack said, a little redundant, but otherwise seems fine.

I do think the entwine cost is a bit high though. 5 mana to end up with basically Murder? (OK, Unmake/Oblivion Strike, but.)

I think it's that "can't search" is such an unusual ability, it's sort of obvious it's here just to power up the first ability (although, as an instant, it's quite strong in its own right).

I often end up writing entwine costs as if they were the whole cost for the combined effect, because the cost for the combination effect often looks wrong with the original cost in it as well. Even though that's not actually how entwine works. If the combined effect is sufficiently more expensive, it doesn't make a lot of difference (as with the best peculiar spells, like Peculiar Distortion). But sometimes, like here, there's no cost that quite looks right to me.

OTOH, it seems straight-up "exile target creature" is quite hard to find. It's on four-cost sorceries, and triple-white or triple-black Unmake, and Brittle Effigy, but is it actually on any other instants cheaper than 6?

My headcanon is that it's like counterspell: it needs triple-white or triple black, else anyone can do it but it's really expensive :)