Of the seven deadly sins, lust is definitely the pick of the litter.

…the sin of gluttony, also the sin of lecherous intent toward an honourable and high-placed matron….But more sin is to come, and that sin a double one, namely of lechery in act, perhaps venial in the young but by no means to be condoned, and of adultery, which Saint John saith shall be punished by fire for the act and brimstone for the stink of the ordure of the partners in that sin….She is but a heathen….With the instinct of her kind she knoweth the best and most secret places for lechery….thou are bent on sin, the act of darkness….On her breath is no honey but the smell of strong drink, the potent mingling of barley and juniper in deadly ferment….One man is from the Antipodes but, contrary to the superstition of the vulgar, he is like other men….It is he who seeth the cabin where thy lust worketh itself out, he remembereth lewd advice of the charioteer of Cathay….approacheth on tiptoe the sound of beastly gratification….Lust croucheth now above in the rooftree, his wings fearfully foldeth….But in his rage he spareth not her, calling her Jezebel and harlot….

By following entirely the guidance of lust, in the manner of fools, man loses his intellectual energy, injures his body, and perishes before his natural time; sighs and cares multiply; there is an increase of envy, hatred, and warfare, for the purpose of taking what another possesses. The cause of all this is the circumstance that the ignorant considers physical enjoyment as an object to be sought for its own sake. God in His wisdom has therefore given us such commandments as would counteract that object, and prevent us altogether from directing our attention to it, and has debarred us from everything that leads only to excessive desire and to lust. This is an important thing included in the objects of our Law.

The Bible says that lust in your heart is committing adultery, so you can't masturbate without lust.

Sex, sin, and the Devil were early linked.

As for the vice of lust - aside from what it means for spiritual persons to fall into this vice, since my intent is to treat of the imperfections that have to be purged by means of the dark night - spiritual persons have numerous imperfections, many of which can be called spiritual lust, not because the lust is spiritual but because it proceeds from spiritual things. It happens frequently that in a person's spiritual exercises themselves, without the person being able to avoid it, impure movements will be experienced in the sensory part of the soul, and even
sometimes when the spirit is deep in prayer or when receiving the sacraments of Penance or the Eucharist. These impure feelings arise from any of three causes outside one's control.

First, they often proceed from the pleasure human nature finds in spiritual exercises. Since both the spiritual and the sensory part of the soul receive gratification from that refreshment, each part experiences delight according to its own nature and properties. The spirit, the superior part of the soul, experiences renewal and satisfaction in God; and the sense, the lower part, feels sensory gratification and delight because it is ignorant of how to get anything else, and hence takes whatever is nearest, which is the impure sensory satisfaction. It may happen that while a soul is with God in deep spiritual prayer, it will conversely passively experience sensual rebellions, movements, and acts in the senses, not without its own great displeasure.

This frequently happens at the time of Communion. Since the soul receives joy and gladness in this act of love - for the Lord grants the grace and gives himself for this reason - the sensory part also takes its share, as we said, according to its mode. Since, after all, these two parts form one individual, each one usually shares according to its mode in what the other receives. As the Philosopher says: Whatever is received, is received according to the mode of the receiver. Because in th

"Every kind of contempt for sex, every impurification of it by means of the concept "impure", is the crime par excellence against life — is the real sin against the holy spirit of life"

I am saying cult. It is a cult of abomination. It is clear that it is abomination. The Torah punishes it with death. This is in the first line of serious sins. They say 'tendency,' 'perversion' -- nonsense. There is lust, and a person can overcome it if he wants, as with any other kind of lust. This is one of the most forbidden types of lust. The most grave.

To a clergyman lying under a vow of chastity any act of sex is immoral, but his abhorrence of it naturally increases in proportion as it looks safe and is correspondingly tempting. As a prudent man, he is not much disturbed by incitations which carry their obvious and certain penalties; what shakes him is the enticement bare of any probable secular retribution. Ergo, the worst and damndest indulgence is that which goes unwhipped. So he teaches that it is no sin for a woman to bear a child to a drunken and worthless husband, even though she may believe with sound reason that it will be diseased and miserable all its life, but if she resorts to any mechanical or chemical device, however harmless, to prevent its birth, she is doomed by his penology to roast in Hell forever, along with the assassin of orphans and the scoundrel who forgets his Easter duty.

André Linoge: Born in lust, turn to dust. Born in sin, come on in!

Of all the horrid brutalities of our age, I know of none so horrid as those that are sanctioned and defended by marriage. Night after night, there are thousands of rapes committed, under cover of this accursed license; and millions— yes, I say it boldly, knowing whereof I speak— millions of poor, heartbroken, suffering wives are compelled to minister to the lechery of insatiable husbands, when every instinct of body and sentiment of soul revolts in loathing and disgust... The world has got to be startled from this pretense into realizing that there is nothing else now existing among pretendedly enlightened nations, except marriage, that invests men with the right to debauch women, sexually, against their wills, yet marriage is held to be synonymous with morality! I say, eternal damnation, sink such morality!

It was only Christianity, with resentment against life in its foundations, which made sexuality something impure: it threw filth on the beginning, on the prerequisite of our life

Yea! as I loath, I lust; I prostitute myself to thee, perversely prurient - Wilt thou not make this night the nameless nuptial, the Devil thy Lord and mine at Our Black Mass?

It is not only when it takes the form of physical addiction that sex is evil. It is also evil when it manifests itself as a way of satisfying the lust for power or the climber's craving for position and social distinction.