I just watched Axelsen's game against Zhengming Wang. I was surprised at how much he has improved his footwork. I watched another video of him practicing with Woong Chong Han from 2 years back and Axelsen's footwork was not very good - it wasn't smooth or balanced. The Denmark coaching staff has really worked on Axelsen's footwork and the difference is very noticeable.
Axelsen's strength is definitely his smash. He is already pretty tall for the pro circuit so his smashes get very good angle. Plus, he has very good power on his smash.
He has three noticeable weaknesses though, compared to the top players. One is his consistency. He hit a few lob shots from the net that were several inches out. He will naturally improve on his consistency with more training and experience so this is not a big issue. His second weakness is his line judgement. There was a shot that Wang hit that was several inches in and Axelsen misjudged it (compare this to Lin Dan who can consistently judge shots to within an inch). His line judgement will naturally improve with more experience so that's not a big deal either.
His third weakness though is his form. The Denmark coaching staff need to fix his form. Axelsen has very stiff form - his form is not fluent or smooth at all compared to say, Peter Gade. Axelsen's form is so stiff, he cannot mask his shots well and the other opponents can read his shots. Ironically, the opposite of Axelsen is Peter Gade who has a very smooth form and is thus deceptive. Peter Gade can still play at the top level at 35 years of age because his form is so natural. But if the Denmark coaching staff can fix Axelsen's footwork, I assume they can eventually fix his form. Maybe they should also have Peter Gade help out in fixing Axelsen's form.
Otherwise, Axelsen has a very bright future in front of him. If he fixes the above 3 weaknesses (better defense would be nice too), I don't see why he can't be a top 10 player or even a top 5 player.
Just wanted to update this. I saw Viktor play against Sho Sasaki recently and he has fixed much of the stiffness in his form. I dare say that he looks fluid now. His footwork looks fine to me now - I can't believe what the Danish coaching staff have done with him!
For Viktor's height, his form, footwork, and balance are amazing. Usually, people as tall as Viktor will have some awkwardness/clumsiness with their form. However, Viktor looks relatively smooth, which is all the more surprising given his height.
Because of Viktor's height, he has a killer half smash (and he knows this is a weapon of his) that is devastating against shorter players. Sho Sasaki struggled against Viktor's half smashes throughout most of the match.
Viktor's main weakness though is experience and consistency. Viktor was leading 20-17 against Sasaki but could not close the deal. Sasaki came back to tie it 20-20 and then win the set. I can guarantee you that LD or LCW would have closed the deal at 20-17 and this is something Viktor has to learn.
I really like Viktor's technique - he has some nice deceptive shots, has a good touch at the net, and actually has a backhand smash too!
Consistency will come with time if Viktor keeps pushing himself to play at the SS and more high level tournaments.
I think Viktor's future is really bright. I can't really think of any singles players at his height that has his technique and footwork. IMO, he has better technique than Chen Long (especially the deceptive shots), but he doesn't have the consistency and experience of Chen Long.
If Viktor keeps working at his game and pushes himself at the SS, I don't doubt that he will be a top 5 player one day and be Denmark's best player - provided he keeps working on his game and finds ways to get better at future international tournaments.