Islam contains absolutely cruel, and unthinkably inhumane punishments for several crimes and even non-crimes. These punishments and teachings in Islam show how fundamentally unfit it is for the modern world.
(I) Theft - Amputation of the hand:
5:38 - As for the thief, both male and female, cut off their hands. It is the reward of their own deeds, an exemplary punishment from Allah. Allah is Mighty, Wise.
Sahih al Bukhari 6799 - Narrated Abu Huraira: Allah 's Apostle said, "Allah curses the thief who steals an egg (or a helmet) for which his hand is to be cut off, or steals a rope, for which his hand is to be cut off."
Sahih al Bukhari 6790 - Narrated Aisha: The Prophet said, "The hand of a thief should be cut off for stealing a quarter of a Dinar."
(II) Fornication and adultery - Hundred lashes in public (plus stoning to death for adultery):
24:2 - The woman and the man guilty of illegal sexual intercourse, flog each of them with a hundred stripes. Let not pity withhold you in their case, in a punishment prescribed by Allah, if you believe in Allah and the Last Day. And let a party of the believers witness their punishment.
Sahih al Bukhari 7332 - Narrated Ibn `Umar: The Jews brought a man and a woman who had committed illegal sexual intercourse, to the Prophet and the Prophet ordered them to be stoned to death, and they were stoned to death near the mosque where the biers used to be placed.
Sahih al Bukhari 2695 - Narrated Abu Huraira and Zaid bin Khalid Al-Juhani: A bedouin came and said, "O Allah's Messenger! Judge between us according to Allah's Laws." His opponent got up and said, "He is right. Judge between us according to Allah's Laws." The bedouin said, "My son was a laborer working for this man, and he committed illegal sexual intercourse with his wife. The people told me that my son should be stoned to death; so, in lieu of that, I paid a ransom of one hundred sheep and a slave girl to save my son. Then I asked the learned scholars who said, "Your son has to be lashed one-hundred lashes and has to be exiled for one year." The Prophet said, "No doubt I will judge between you according to Allah's Laws. The slave-girl and the sheep are to go back to you, and your son will get a hundred lashes and one year exile." He then addressed somebody, "O Unais! go to the wife of this (man) and stone her to death" So, Unais went and stoned her to death.
Sahih Muslim 4191 - 'Ubada b. as-Samit reported Allah's Messenger (may peace be upon him) as saying: "Receive (teaching) from me, receive (teaching) from me. Allah has ordained a way for those (women). When an unmarried male commits adultery with an unmarried female (they should receive) one hundred lashes and banishment for one year. And in case of married male committing adultery with a married female, they shall receive one hundred lashes and be stoned to death."
(III) Homosexuality - death; and transgenders - forcing them out of their homes:
Quran 7:80 to 7:84 - And (remember) Loot (Lot), when he said to his people: ‘Do you commit the worst sin such as none preceding you has committed in the ‘Aalameen (mankind and jinn)? Verily, you practise your lusts on men instead of women. Nay, but you are a people transgressing beyond bounds (by committing great sins).’ And the answer of his people was only that they said: ‘Drive them out of your town, these are indeed men who want to be pure (from sins)!’ Then We saved him and his family, except his wife; she was of those who remained behind (in the torment). And We rained down on them a rain (of stones). Then see what was the end of the Mujrimoon (criminals, polytheists and sinners)”
Sunan Abu-Dawud 4462 - Narrated Abdullah ibn Abbas: The Prophet said: If you find anyone doing as Lot's people did, kill the one who does it, and the one to whom it is done.
Sahih al Bukhari 5886 - Narrated Ibn `Abbas: The Prophet cursed effeminate men (those men who are in the similitude (assume the manners of women) and those women who assume the manners of men, and he said, "Turn them out of your houses."
(IV) House arrest for life for women committing "sexual immorality/lewdness":
4:15 - If any of your women are guilty of lewdness, Take the evidence of four (Reliable) witnesses from amongst you against them; and if they testify, confine them to houses until death do claim them, or Allah ordain for them some (other) way.
(V) Beating people who consumed alcohol:
Sahih al Bukhari 6777 - Narrated Abu Salama: Abu Huraira said, "A man who drank wine was brought to the Prophet. The Prophet said, 'Beat him!" Abu Huraira added, "So some of us beat him with our hands, and some with their shoes, and some with their garments (by twisting it) like a lash, and then when we finished, someone said to him, 'May Allah disgrace you!' On that the Prophet said, 'Do not say so, for you are helping Satan to overpower him.' "
(VI) Crucifixion, chopping off hands and feet and other forms of torture:
5:33 - The only reward of those who make war upon Allah and His messenger and strive after corruption in the land will be that they will be killed or crucified, or have their hands and feet on alternate sides cut off, or will be expelled out of the land. Such will be their degradation in the world, and in the Hereafter theirs will be an awful doom.
Sahih al Bukhari 3018 - Narrated Anas bin Malik: A group of eight men from the tribe of 'Ukil came to the Prophet and then they found the climate of Medina unsuitable for them. So, they said, "O Allah's Messenger! Provide us with some milk." Allah's Apostle said, "I recommend that you should join the herd of camels." So they went and drank the urine and the milk of the camels (as a medicine) till they became healthy and fat. Then they killed the shepherd and drove away the camels, and they became unbelievers after whey were Muslims. When the Prophet was informed by a shouter for help, he sent some men in their pursuit, and before the sun rose high, they were brought, and he had their hands and feet cut off. Then he ordered for nails which were heated and passed over their eyes, and whey were left in the Harra (i.e. rocky land in Medina). They asked for water, and nobody provided them with water till they died (Abu Qilaba, a sub-narrator said, "They committed murder and theft and fought against Allah and His Apostle, and spread evil in the land.")
CONCLUSION: We can all argue if some of these actions are moral or immoral, but the fact is that the level of punishment is disproportionate and inhumane. Chopping off hands for theft condemns the thief with a punishment that he or she can never recover from. Publicly humiliating people with 100 lashes or stoning to death are absolutely savage. If you ever watched a video of a person being stoned to death anyone with a heart would see how utterly devoid of humanity such a punishment is for any crime. The LGBT are clearly going to suffer, whether by being put to death or being rendered homeless. Apart from that, no civil society should recognize torture as a valid punishment for any crime. These aspects of Islam should make any believing Muslim rethink whether Islam is a great religion, to say the very least.