What is the difference between greed and karma? For instance, a person eats meat greedily, greed for meat but no direct killing. Another person kills a cat (not for food) but he is not greedy. Which one is more unwholesome or causing more suffering, killing or greed?
Greed is one of the 3 defilements that causes bad Karma. The other 2 are aversion and ignorance. A greedy thought is bad Karma.
Killing is caused by aversion. It is more unwholesome and causes more suffering compared to craving for the taste of meat. Because killing breaks the first precept.
Why seaching after better evil? Why not striving for abstain of evil and follow what one him/herself wouldn't harm?
How can there be killing, harming life, without greed, desire, thirst (tanha), caving after sensual pleasure, becoming, not-becoming/being?
Killing and taking of what is not given, abuse and lying, speaking untrue and for a favour, always involves desire for one or another food (joy from physical nurishment, touch/contact, intellectual intention, consciousness). Just look attentive. That's corruption (duṭṭha), nothing else. Don't feed corruption in ways of thinking, in ways of association, nurishment and entertainment.
Why seek for better foolishness and don't go after the wise? What does one expect on such looping tracks of views and stands. Dhamma is simple: abstaining from harming life is skillful and beyound that, in this regard, there is no good. Entertaining ones intellect? Such causes a lot of pain, for one self and many.
There is no such as aversion and in it's extrem killing when there is no such as big greed and love (tanha for sensuality, becoming, not becoming/being) on first place. And there is no such as greed if there is not strong delusion at first place, wrong view, not-knowing.
Hatred, aversion, is "just" the other side of love, the twin brother, honey (his poision) for the fool:
thinking, 'O, that what belongs to others would be mine!' He bears ill will, corrupt in the resolves of his heart: 'May these beings be killed or cut apart or crushed or destroyed, or may they not exist at all!' He has wrong view, is warped in the way he sees things: 'There is nothing given, nothing offered, nothing sacrificed. There is no fruit or result of good or bad actions. There is no this world, no next world, no mother, no father, no spontaneously reborn beings; no brahmans or contemplatives who, faring rightly & practicing rightly, proclaim this world & the next after having directly known & realized it for themselves.' This is how one is made impure in three ways by mental action.
So at least it's all a matter of how strong delution is, how obviously basic right view.
On it wrong resolve/intent/will is based, which is base of actions by body, signs, thoughts.
"And what is right resolve? Being resolved on renunciation, on freedom from ill will, on harmlessness: This is called right resolve.
It's not possible to kill (by one self, bodily), order to kill (speech, signs), or approve killing of what ever being (thoughts of agree, acceptance, joy for benefit of what one regards as own, or good, e.g. killing the "bad" is also forced by selfidentification, desire), for what ever purpose, without strong unskillful mind (connected with greed, aversion, delusion), without strong effects and causes.
"Bhikkhus, followed by those three things, one is headed and designated for hell. Which three? One self takes life, instigates others to take life, and approves taking of life. These, Bhikkhus, are the three things, of which one is headed and designated for hell."
"One self speaks what is not true, instigates others to speak what is not true, and approves speaking of what is not true..."
"One self abstains from speaking of what is not true, instigates others to abstain from speaking of what is not true, and approves abstaining from speaking of what is not true..."
"One self has wrong view, instigates others to wrong view, and approves wrong view..."
"One self has right view, instigates others to right view, and approves right view. These, Bhikkhus, are the three things, of which one is headed and designated for heaven."
"Bhikkhus, I do not know anything else that arouses non arisen merit  and fades arisen demerit as good companionship. Good companions arouse non arisen merit and fades arisen demerit. This is the first.
"Bhikkhus, I do not know anything else that arouses non arisen demerit and fades arisen merit as evil companionship. Evil companions arouse non-arisen demerit and fades arisen merit. This is the second.
- "Bhikkhus, those who point out wrong Dhamma as Dhamma, Bhikkhus, those archive harm for many people, suffering for many people, for the sorrow and suffering of heavenly and human beings. Much demerits, Bhikkhus, those produce, for the disappearing of the true Dhamma.
Truly unfortunate are many if looking with whom and where they associate, what they pay rebut to... May they work on their ways out!
Because beings, not arrived at Dhamma yet, are unable to distinguish between defiled and right judgment of what is intention, of what quality the mind actually is, one does good to stick simple by "not taking life/destroy life/take existence of beings" (of what ever kind they came into being, by oneself, in order, or agree). Later it will be not different but just naturally. Such ideas of doing bad might be good are ideas of fools who are good to be avoided striktly.
Not consorting with fools, consorting with the wise, paying homage to those worthy of homage: This is the highest protection.highest protections/blessings
Kill possible all notions to associated, assist, approve, nurish, accept and entertain (upadana) toward actions and signs of them inwardly and before outwardly to success. This is the kind of aversion and disgust the wise approve, like to be extrem "greedy" after liberation, after right view and not getting lost in a thicket of wrong views and improper attention.
"What do you think Dhanañjani? There is the case where a certain person, for the sake of his mother & father, does what is unrighteous, does what is discordant. ...for the sake of his wife & children ... his slaves & workers ... his friends & companions ... his kinsmen & relatives ... his guests ... his departed ancestors ... the devatas ... the king, does what is unrighteous, does what is discordant...for the sake of refreshing & nourishing his body, does what is unrighteous, does what is discordant. Then, because of his unrighteous, discordant behavior, hell-wardens drag him off to hell. Would he gain anything by saying, 'I did what is unrighteous, what is discordant, for the sake of refreshing & nourishing my body. Don't [throw] me into hell, hell-wardens!' Or would others gain anything for him by saying, 'He did what is unrighteous, what is discordant, for the sake of refreshing & nourishing his body. Don't [throw] him into hell, hell-wardens!'?"
"No, master Sariputta. Even right while he was wailing, they'd cast him into hell."...
"Dhanañjani, there are other activities — reasonable, righteous — by which one can refresh & nourish one's body, and at the same time both not do evil and practice the practice of merit."
[Note: This is a gift of Dhamma and not meant for commercial purpose or other low wordily gains by means of trade and exchange.]
I used to fantasize about killing my neighbor's cats (because the cats killed the native birds in my garden & killed some small native trees I planted). I used also fantasize about killing my neighbor's dogs because they bark at night & bark at people, unnecessarily. However, fortunately, at least one of the neighbor's dogs killed one of the neighbor's cat so now there is only one cat.
Buddhism teaches kamma is intention and the results of kamma (action) depend on the quality of the intention. Killing motivated by greed or hatred generates a negative result. But killing from a good intention (such as to save native birds & trees) does not generate a negative result.