It’s right at the edge, depends on the battery being charged. The +12V output rating of 4.5A is 54 watts (12V x 4.5A). The charger consumes some power in addition to the output, might be dicey to get the full 50W output reliably. Generally a modern charger will consume 10 to 20% (efficiency of 80 to 90%).

But if charging a 2S lipo, the charger will only have 42 watts of output due to the 5 amp limit (8.4V peak voltage x 5A). Should be OK, but not much extra for a safety margin. If you convert it watch temps carefully for the first few charges.

Also be aware PC supply conversions vary in their ability to maintain a useable voltage at full power.

Larger PC supplies are fairly plentiful and not terribly expensive, especially if you can find some used ones for cheap or even free, might be worth finding something bigger before putting the effort into converting it for RC use.