To be honest it is a difficult task, if done perfectly. Though you can get a general view according to ascendant, that the trine lords are always favourable and trik (6, 8 & 12) lords are unfavourable. But considering these lords are just one of the factors to know about good & bad planets.
There are at least 15 factors to know exactly about the good and bad planets in a horoscope. Few of them are very advance one. I am only sharing very important and significant factors which help to know about good & bad planets of a horoscope.
Basic important factors:
- Lord of 3rd, 6th and 11th house are malefic. Planet in the 11th house is not a bad thing but the lord of the 11th is really a bad planet. 8th lord is very neutral, if 8th lord is also the lord of 3rd, 6th and 11th house then it is very malefic and if it is the lord of trine or 1st, 5th and 9th then mostly benefic. You have to check it in divisional charts and make a conclusion of it. Means if the planet becomes malefic with this factor in D-1 and becomes malefic in D-9 & other divisional charts too, then it is most malefic. Similarly make your conclusion.
- A debilitated, enemy sign status of a planet reduces its beneficence. Exalted, friendly, own sign status boosts beneficence.
- Planet in Rahu-Ketu axis also reduces its beneficence. Also, if aspected by malefic Saturn-Mars. Aspected by natural benefics are good.
- Saturn-Mars becomes more malefic if retrograde or combust or both. Even benefic planets if combust or retrograde loses their some beneficence. But if lord of malefic houses are combust then good results are experienced.
- The Planets in mrityu bhaga are bad. Planets in pushkara bhaga are good, pushkar navamsha only adds extra strength for good or bad results.
- Planets in gandanta are bad.
- Planets in nakshatra of Ketu show some debt, and bad. But, also look at Ketu in the chart, if well placed then it is for good.
- Planets in daridra or arishta yoga are bad. Planets in rajyoga and dhana yoga are good.
- Planets occupying navamsa sign which is trik (6, 8 & 12) sign of D-1 are bad. For ex: Moon in taurus sign in navamsa and D-1 lagna is Sagittarius. So, the moon will fall in the 6th house. Similarly if it falls in trine of D-1 then good.
- Planets in surya hora in D-2 are cruel ones. Whereas moon hora gives smooth results.
Note: If any planet satisfies a type of situation then that adds those qualities more.
Little advance factors:
- Lord of 22nd drekkana and 64th navamsa is malefic. 22nd drekkana from lagna should be seen. 22nd drekkana is nothing but 8th lord from D-3 chart. 64th navamsa lord is 4th lord from moon in navamsa. Though few take 4th lord from navamsha lagna but 4th lord from navamsa moon should be taken. Now, if the above factors makes any planet malefic & that planet also holds this factor then it is more malefic, similarly it will reduce the beneficence of benefic planets.
- Planet in fixed & movable sign and also in sign of 5th or 9th lord of D-1 are good. For ex: D-1 is gemini lagna and Saturn in libra sign in navamsha, now this Saturn is in movable sign and in 5th sign of D-1 too.
- Planet in sarpa drekkana is bad. Basically, see the D-3 chart and any planet in scorpio sign.
You can add Jaimini astrology as well. And can conclude out of it, like if a planet is Gnatikaraka then it adds extra maleficence, similarly a Putrakaraka will add beneficence.
Now from all these above factors, if someone’s Venus satisfies them for bad results. Then it is the most malefic planet. So he/she should do good karma or deeds associated with Venus.
Planets are nothing, only shows our deeds results of many past lives. If someone’s Venus is bad means they must have done bad deeds related to natural and functional signification related to it in the birth chart. Ex: If Venus is 5th lord then it may mean he/she had killed or done something wrong to a female child.
Generally, one should improve his/her deeds in this life for their crippled planets. This is the best remedy.