The parallel passage in luke, calls the great tribulation, the great distress, wrath on this people, and days of vengeance.
Matthew 24:15-21
15So when you see standing in the holy place ‘the abomination of desolation,’adescribed by the prophet Daniel (let the reader understand),
16then let those who are in Judea flee to the mountains.
17Let no one on the housetop come down to retrieve anything from his house.
18And let no one in the field return for his cloak.
19How miserable those days will be for pregnant and nursing mothers! 20Pray that your flight will not occur in the winter or on the Sabbath. 21For at that time there will be great tribulation, unmatched from the beginning of the world until now, and never to be seen again.
Luke 21:20-23
20But when you see Jerusalem surrounded by armies, you will know that her desolation is near. 21Then let those who are in Judea flee to the mountains, let those in the city get out, and let those in the country stay out of the city. 22For these are the days of vengeance, to fulfill all that is written.
23How miserable those days will be for pregnant and nursing mothers! For there will be great distress upon the land and wrath against this people.
Christ warns to flee this great distress/tribulation and indicates one should pray to be worthy to escape it.
Luke 21:36
36So keep watch at all times, and pray that you may have the strength to escape all that is about to happen and to stand before the Son of Man.
Mark 13:14-19
14So when you see the abomination of desolation
a standing where it should not be
b (let the reader understand), then let those who are in Judea flee to the mountains.
15Let no one on the housetop go back inside to retrieve anything from his house.
16And let no one in the field return for his cloak.
17How miserable those days will be for pregnant and nursing mothers!
18Pray that this will not occur in the winter.
19For those will be days of tribulation unmatched from the beginning of God’s creation until now, and never to be seen again.