Back before the Grande ordered the Class 125's the biggest was the Class 70's for helpers, used on the head of the Class 47's on grades such as Marshall, Poncha, Cerro etc. Pictures previously posted on here show Class 60's helping 47's and on the head to boot.
NZR didn't apparently bother with such frivolity.
Here is an X Mountain banking a W
W tanker, the X in Vauclain configuration put out 31,150Lbs TE and the tanker a mere 16,910lbs TE.
Steam locomotive hauling a goods train, passing beneath an overhead bridge.. Ref: APG-1993-1/4-F.
Alexander Turnbull Library, Wellington, New Zealand. /records/22806910