First of you all should know that, every planet has only 3 major roles in every horoscope: To create, to nurse and to destroy. And the planet never misses it.
Because if 5th house is a good house but it is bad for your mother as well, killer of 4th house. And if 6th is bad for you but is your servant as well or profession of your father, so it has to be good for his own profession and his profession will affect you too.
In this way, all the houses and lords have all three major roles in the birth chart in some way. But, the difference is between the forces, who is more destructive and who is more creative.
Vedic astrology is not a general subject. It is very specific and has many variations. Any combination like: Budh-Aditya yoga or Gaj-Keshari etc can have twenty thousand plus variations. And that makes a difference in results and prediction.
Retrograde and Debilitated planets are not harmful, unless they are afflicted or placed without any help, especially debilitated planets.
Now, you should check in the birth chart, which debilitated or retrograde planet is good or which not. Though this deduction is not easy and varies chart to chart but I am giving major rules to find it.
Retro planets are very important to be successful and courageous. And they are found in charts of successful people. Retro planets have good and even high chesta bala, then the normal planets. Because retro planets are close to earth and thus affects more.
Major principle for retro planets is that they give opposite results as per their placement, i.e. if well placed then bad results and if bad placed then good results. Now, the aspect of malefic and becoming bad is avoided.
Bad means, if an exalted planet is well placed and retrograde then it will give bad results and a debilitated planet is such a condition is good. But if retro debilitated planet’s debilitation is canceled then he will give bad results and similarly exalted will give good results.
If the planet is not exalted/debilitated or its own house, then retrograde planet gives good results for that house from which it is bad placed, vice-versa.
Note: This is possible only with 5 planets, not with luminaries or Rahu-Ketu.
Debilitated planets are a blessing nowadays. They tend to work hard, to tackle the current cheating market, which gives them the ability to cheat. But whether a person is cheating for good cause or bad, it depends.
But debilitated planets are harmful, if placed without help or afflicted. I am giving few major rules to determine whether it is good or bad.
When debilitation is canceled they form a great raj-yoga, but should be direct.
Debilitated planets should be well placed in vargas or divisional charts.
If they are debilitated in 3rd, 6th or 8th houses, good.
If they are the lords of 6th, 8th or 12th house again good.
So, you can apply given rules and can deduce whether they are good or bad.