The following is not a word-by-word translation. I will try to convey the meaning.
What is the “great danger (“mahabbhayan“)” (in the rebirth process)?
The great danger is suffering (in the rebirth process).
Suffering is two-fold: physical (felt by the body) and mental.
– Physical suffering is pain (due to injuries, sicknesses, etc.)
– Mental suffering is “domanassa vedana” arising in mind.
Suffering is three-fold: Dukkha dukkhatā, saṅkhāra dukkhatā, vipariṇāma dukkhatā.
– From those three, “the great danger” is “saṅkhāra dukkhatā.”
– That is because the rebirth process is maintained by saṅkhāra generation (via “avijjā paccayā saṅkhāra.”) Thus, once overcoming the saṅkhāra dukkhatā the other two are also removed, and one will get to Nibbāna (Saṅkhāradukkhatāya pana loko anupādisesāya nibbānadhātuyā muccati,)
The post that discusses the three types of suffering is: “Introduction -2 – The Three Categories of Suffering.”