Despite the prevailing obsession around it, remember that no such house in astrology is bad in itself, including the notorious 8th. There are some houses that are “more prone to becoming afflicted” just like there are some planets “more prone to becoming weak/malefic” easily. If there is a person who is allergic to chilies, he would be “more prone to getting sick” when he eats a chilly. But that does not mean that the person is necessarily sick.
Moon and Rahu are the most prone to affliction in the 8th house. In majority of the cases, they are bad in the 8th house because they tend to get afflicted pretty easily when placed in the 8th. This can happen even if they are in friendly signs, well placed, or unaspected by malefics. Slightest affliction to Moon and Rahu placed in the 8th house, creates major negative results.
Saturn and Sun are the least likely to get afflicted in the 8th house. They are the most immune to afflictions there, usually end up contributing significantly to longevity and good health.
Conjunctions in the 8th house usually do have a tendency for creating malefic results subject to the extent of affliction.
As far as house lords are concerned, Moon’s lordship are the most prone to 8th house afflictions followed by 9th house and 7th house. Lagna lord gives its result as per the strength in the sign of the 8th house and the conjunction influences.
With respect to the dasha results, the dasha of a planet in the 8th house is usually bad unless the planet associates with at least one kendra/trine houses.
A dominant 8th house denotes upheavals. It can lead to either a massive rise or a major fall in life. From a health perspective, it can either give chronic suffering, or a very long life. Financially, it can bring abundant gains or profound losses; all depending on the 8th house.
Some of the strongest horoscopes in the world have belonged to people with a lot of planets in the 8th house.
Note: The above first appeared in the form of a Quora Post on April 21, 2019 as a response to the question: Is any planet bad in the 8th house? https://qr.ae/pN9iPX