240v to 120v by using only one leg?
You would first need to change the breaker from 50A to 15A.
Your 50A circuit needs to be one with a neutral (in terms of a typical range outlet, a 4-prong, not a 3-prong.)
At that point, not a problem (assuming you are on normal USA/Canada 120/240 split-phase, 120V to neutral power.)
However, you might find more use in putting a sub-panel fed by the 50A breaker, which could then have the 15A breaker you need to protect your load (which you cannot just hook up to a 50A breaker directly.) You could power multiple other things from the sub-panel, if you have other things to power.
&quot;Current imbalance&quot; is not a concern - you have that any time you have a single 120V load running, and it's mostly a consideration when you have two such loads that you expect to be on at the same time, in which case, it's good to put them on opposite hots.