to lean over (and cover with one's body); to bend over (someone); to (stand tall and) lean on (someone)
to weigh on one; to bear (heavily) on one; to lie on one
彼は私にのしかかってきた。
He leaned over onto me.
責任が重くのしかかる。
Heavy responsibility weighs on me.
借金がのしかかって辛い。
The debt weighing on me is painful.