Many figure collectors may experience a leaning figure in their collection from time to time.
Here is some low down that I got from Modeller T last Sunday. There are different grades of figure factories in China (mainly in Shenzhen). The cost per unit goes up with higher grade factories. So if you are going to give away a freebie with a magazine ( like this figure of Kujo Hachie ) then you will want to keep the cost low.
Cost goes up when the body and arms are made of PVC and leg parts of ABS. The strong ABS usually prevents figures from leaning even if they are standing on one leg.
In this case, I guess the figure was designed with too much weight distributed towards the front of the figure + cheap unit cost = leaning.
So what can I do about it? Well I do what I did to my leaning star wars figures and take a hairdryer to the legs.
Once the legs start to turn black and you start to smell burning plastic, then you can kiss your figure goodbye.
Only heat the legs until they are bendy ^^;