Feat: https://youtu.be/vGN0PKPWTOE?t=221
https://makeagif.com/gif/nights-journey-of-dreams-helens-story-part-9-vs-queen-bella-e2qvIA
NiGHTS is capable of lifting a metal ball with one arm outstretched in a place with a visibly at least comparable to Earth gravitational pull on its surface going by Queen Bella's rapid fall during their defeat there, which would be located in Queen Bella's dream world they made to fight NiGHTS in.
NiGHTS height is revealed to be exactly 150 cm tall, according to their cameos done by SEGA, their creator, with their guest appearance taking place within Sonic Riders:
NiGHTS height = 1.5 meters = 78.16009 px
Metal ball diameter = 117 px
Metal ball radius = ((117/78.16009) *1.5 ) / 2 = 1.12269574 meters
Metal ball volume = (4/3)*pi*(1.12269574^3) = 5.92754464 m^3
From the appearance of the spherical ball chunk originating and flung falling from one of the metallic looking platforms and being changed into being magically larger by NiGHTS' paraloop before its lifted and thrown, I will assume it to be made of bronze which has a density of about 8150 kg/m^3 on average: https://www.researchgate.net/figure/Typical-examples-of-force-displacement-curves-a-Force-elongation-measurements-of-the_fig1_320490612
Metal ball mass = 8150 * 5.92754464 = 48309.4888 kg
or 48.3094888 metric tons
Which is Class 50 Lifting Strength.
However, this was lifted and seemingly thrown with just one arm.
Considering that, their lifting strength using both arms should be = 47420.3571 * 2 = 96618.9776 kg
or 96.618.9776 metric tons
Which is Class 100 Lifting Strength