Sadhu Sundar Singh (who personally met Lord Jesus Christ supernaturally) believed in these Biblical doctrines even toward the end of his mysterious disappearance into the Himalayas somewhere around 1929:
(1) Trinity is True.
(2) Universalism in Christ alone is Biblical, True & is the “secret” of God Himself through His Son.
Many visions & supernatural insight speak of these though many “modern day biographers” (who didn’t know him personally – ‘skip’ these parts probably to make him look like he’s part of the eternal-hell camp or to make “more sales” (more money) by sticking to a more neutral write-up which may cater to a larger audience).
(3) There is punishment in the afterlife but it is “not eternal” but to the “age to come” (for men) or “ages to come” (demons & the rest) according to the malice done.
I personally believe in these facts myself even as both my less significant bad spiritual experience as well as my literal reading of the Bible (closest translation to expound the meaning of the Original Biblical manuscripts) seem to agree and point to this direction of “truth”.
Lastly, this point of concurrency certainly implies that Sundar Singh and I must be speaking or are in a relationship with the “same” Lord Jesus Christ.
Here is an example of his more authentic biography or message in Christ:
Those Christians who “deny the Trinity” usually have one thing in common: “None” of them have a direct ‘authentic’ supernatural or spiritual encounter with respect to Lord Jesus Christ.
Thus their denial arguments (which I’ve easily refuted many times with Scripture stating the opposite, literally too – an archive of it may be found in the links below) is “carnal” and has no “supernatural” evidence (such as, has Christ the Lord appeared to you and denied that He is God? I guess not; plenty of supernatural encounters have confirmed otherwise across the spectrum of Christianity).