I see both the Bab and Baha'u'llah are the return of Christ. There is always someone that prepares the way, as Elijah always comes first.
You quote Malachi, but is it in context?
Malachi 2:11 Judah has been unfaithful. A detestable thing has been committed in Israel and in Jerusalem: Judah has desecrated the sanctuary the Lord loves by marrying women who worship a foreign god. 12 As for the man who does this, whoever he may be, may the Lord remove him from the tents of Jacob[
c]—even though he brings an offering to the Lord Almighty.
3:1 “I will send my messenger, who will prepare the way before me. Then suddenly the Lord you are seeking will come to his temple; the messenger of the covenant, whom you desire, will come,” says the Lord Almighty.
2 But who can endure the day of his coming? Who can stand when he appears? For he will be like a refiner’s fire or a launderer’s soap. 3 He will sit as a refiner and purifier of silver; he will purify the Levites and refine them like gold and silver. Then the Lord will have men who will bring offerings in righteousness, 4 and the offerings of Judah and Jerusalem will be acceptable to the Lord, as in days gone by, as in former years.
5 “So I will come to put you on trial. I will be quick to testify against sorcerers, adulterers and perjurers, against those who defraud laborers of their wages, who oppress the widows and the fatherless, and deprive the foreigners among you of justice, but do not fear me,” says the Lord Almighty.
4 “Surely the day is coming; it will burn like a furnace. All the arrogant and every evildoer will be stubble, and the day that is coming will set them on fire,” says the Lord Almighty. “Not a root or a branch will be left to them. 2 But for you who revere my name, the sun of righteousness will rise with healing in its rays. And you will go out and frolic like well-fed calves. 3 Then you will trample on the wicked; they will be ashes under the soles of your feet on the day when I act,” says the Lord Almighty.
4 “Remember the law of my servant Moses, the decrees and laws I gave him at Horeb for all Israel.
5 “See, I will send the prophet Elijah to you before that great and dreadful day of the Lord comes. 6 He will turn the hearts of the parents to their children, and the hearts of the children to their parents; or else I will come and strike the land with total destruction.”
Is Malachi warning them about somethings a couple of thousands of years later?
Or... Is this a warning to the people at that time?