In Islam there are 2 kinds of killing:
The forbidden one is the taking away of innocent lives which is harshly condemned by Allah ﷻ and if anyone does it then they will be punished in the hereafter had they not been punished in this life or repented before death: (Al Quran 5:32) "if anyone slays a human being unless it be [in punishment] for murder or for spreading corruption on earth - it shall be as though he had slain all mankind; whereas, if anyone saves a life, it shall be as though he had saved the lives of all mankind."
The one in which Muslims are encouraged to kill, and get killed, is when fighting against injustice and oppression, for the sake of truth and justice, and this is considered fighting in the way of Allah ﷻ. The characteristics of such persons are mentioned in the Quran:
‘(Al Quran 9:111–112) BEHOLD, God has bought of the believers their lives and their possessions, promising them paradise in return,[and so] they fight in God's cause, and slay, and are slain: a promise which in truth He has willed upon Himself in [the words of] the Torah, and the Gospel, and the Qur'an. And who could be more faithful to his covenant than God? Rejoice, then, in the bargain which you have made with Him: for this, this is the triumph supreme! [It is a triumph of] those who turn [to God] in repentance [whenever they have sinned], and who worship and praise [Him], and go on and on [seeking His goodly acceptance], and bow down [before Him] and prostrate themselves in adoration, and enjoin the doing of what is right and forbid the doing of what is wrong, and keep to the bounds set by God. And give you [O Prophet] the glad tiding [of God's promise] to all believers.
As per Quran and Hadith the characteristics of Muslims who kill and are killed in the way of Allah ﷻ are quite evident. They will definitely and without a doubt get many blessings in the hereafter. The example of such Muslims can be presently found Rohingya of Myanmar killed by extremist Buddhists, Muslims of Kashmir who are fighting the oppressing Indian Army for more than 70 years. Such example can be found in the innocent Palestinians who are fighting the Israeli oppressors or such as those of Afghanistan who are fighting the invaders.
What is the greatest desire of those martyred in the way of Allah ﷻ?
To the surprise of many the greatest desire of those who fight and are killed in the way of Allah ﷻ is actually not females but in fact something else and this is recorded as per authentic hadith:
".....that their souls (those who are killed in the way of Allah) are in green birds wandering in Paradise wherever they wish, returning to lamps hanging from the Throne. Your Lord looks at them and says: 'Do you want anything more that We may grant you more?' They say: 'Our Lord! What more could we have when we are in Paradise wandering wherever we want' Then He looks at them a second time and says: "Do you want anything more that We may grant you more?' When they realize that they will not be left alone with that, they say: 'Return our souls to our bodies, so that we may return to the world to be killed in Your cause another time.'" - This status of the martyrs shared by Prophet Muhammad ﷺ makes it absolutely clear that the greatest desire for martyrs killed in the way of Allah ﷻ is not women but in fact to be returned to earth and once again be killed for Allah's sake. This is due to the immense spiritual blessing that they receive at the point of their deaths that no other experience, even that of the enormously beautiful females of paradise can surpass it!
What do the martyrs killed in Allah’s path get in paradise?
There are a list of benefits in the authentic narrations that a martyr killed in the way of Allah ﷻ gets and these are blessings which we are thankful to Allah ﷻ: Messenger of Allah ﷺ said: "There are six things with Allah for the martyr. He is forgiven with the first flow of blood (he suffers), he is shown his place in Paradise, he is protected from punishment in the grave, secured from the greatest terror, the crown of dignity is placed upon his head - and its gems are better than the world and what is in it - he is married to seventy two wives along Al-Huril-'Ayn of Paradise, and he may intercede for seventy of his close relatives." - Certain things need to be noted about this hadith: First, its not only wives from among the beautiful maidens of paradise that martyrs will get but its also the forgiveness, the great honor in the sight of Allah ﷻ which makes them desire to live again and fight for Allah’s sake. Additionally his life in grave and hereafter becomes peaceful and also the martyr will get to intercede for his loved ones on the judgment day through the honor that he may have achieved. Only a foolish Muslim who while believing in the hereafter would deny such blessings.
The main thing to learn is that the figure "seventy one" or "seventy two" or "seventy three" in Arabic language is not to teach us an exact figure, it is to be noted that the term "seven" or "seventy" in Arabic also means "several" or "multifold". Therefore what is being taught is not a figure but a blessings multiplied in terms of whatever the martyr will get which includes women of paradise!
Why do martyrs or paradise dwellers get so many wives and hoor al ayn (maidens of paradise) such as Seventy or more than Seventy?
The term seventy two or seventy is not just a mere accident of words, in fact it informs the Muslim believers about a great and beautiful fact about the gender ratio in paradise. The following authentic recorded hadith sheds light on this for us: Allah's Messenger ﷺ said, "The first group (of people) who will enter Paradise will be (glittering) like the moon when it is full…..Everyone of them will have two wives; the marrow of the bones of the wives' legs will be seen through the flesh out of excessive beauty..” - If every male believer gets 2 wives in paradise in addition to the number of hoor al ayn (paradise maidens) which number up to seventy or more than seventy for honored ones such as martyrs, then this clearly indicates that women are more in paradise than males. As per many famous Imams of the majority Ahle Sunnah (Sunni) school of thought the above hadith informs us that majority dwellers of paradise are women and therefore they will be naturally given to the males in paradise as they being women also desire males.
The Hoor Al Ayn (Maidens of paradise) also desire the Muslims just like Muslims desire them
The ahadith that speak about martyrs or male believers getting "beautiful maidens" does not mean in any way that females of paradise, whether from those of earth or from among the residents of paradise, are given away without their consent. An authentic hadith of the Prophet ﷺ clearly states that these maidens are longing to be with the believers every day and pray to Allah ﷻ for that communion: Messenger of Allah ﷺ said "Indeed in Paradise there is a gathering for Al-Hur Al-'Ein wherein they raise their voices. The creatures have not heard the likes of them." [He said:] "They say: 'We are the eternal ones, we shall not die. We are the ones who live in joy and comfort, we have no needs. We are the pleased ones, we do not get angry. Tuba (good news) to the one who belongs to us and we to him.'"
Last but not least its quite obvious that a man who died for Allah’s sake will get women in paradise due to him being a male and naturally a male desires a female. If Allah ﷻ wishes to give such martyrs beautiful women and paradise maidens who also desire their male counterpart, in addition to other unimaginable blessings, then who are we to question or show reservations? We gladly accept it!
May Allah ﷻ guide the apologetic Muslims who deny in their ignorance the blessings of their Deen.
 Jami Tirmidhi - Vol. 5, Book 44, Hadith 3011
 Sahih al-Bukhari 3245
 Jami at-Tirmidhi 1663
 Jami at-Tirmidhi Vol. 4, Book 12, Hadith 2564