Yes, 100% you can complete these events without buying anything from the shop.  You just need to save up energy.  Once you reach your max energy then you won't regen anymore, but each time you get an energy refill (such as after 60 mins of gametime each day) it'll top you up by your current max energy (e.g. if your max energy is 130, then each energy refill you get adds +130 energy).  This means that you can be 10,000/130 energy, which is 10,000 energy with a max energy of 130

I mentioned this in another thread but you can get about 17,000 energy a month by spending the bare minimum of gametime.  I had 18,000 energy when I started the Brogni event and finished at about 8,000 when it was complete.

If you're asking if you can complete it just by the daily refills, then no.

No, you cannot.

The events are purposefully designed to make people spend money to get the fusion champions.

In theory, you can basically not play the game and only harvest resources between the fusions. But this time even that wasn't enough. You can only save up close to 14K energy each month and with how ridiculously impossible the milestones were you burned through that not even knowing how. Like I burned 7K running a campaign for the levelling event and it wasn't enough. 

And even if it was possible, it is a really stupid game design.

Of course you can - if you save all the free energy refills you get from daily gifts and only spend them during special occasions like fusions. You certainly need to spend a whole bunch of refills during a fusion event, so if you don't save the free ones, then you'd have to buy them with gems. Which is how it used to go in the past before they started handing out all those free refills - the points required were lower, but we actually had to pay gems for all the refills. 

It's not the Developers Job to answer you.

The game has a system in place to deal with Questions & Answers.

Not a dev, but fusions are doable with just the free resources you can earn within the game. The last fusion was hard, yes, but it was still manageable if you had prepared and managed your resources well (saved gems, gift energy refills, shards) prior to the fusion. 

This is a lie, people playing for 1-6 months minimum, unable to accumulate as many fragments as necessary for your greedy mergers

buy a monthly gem card for 999 per months thats round 2100 or more gems per months then with resorces on top its easy ) this what i do ) IM sure there is other ways to do that but u will need to skip fussions to save energy !

Developer won't answer it, admin can, some old players can, I can. 

L9753 gave the right answer.

P/S: Plarium is no charity group, they do business, they need money, free players can't expect too much from any business, they can give you free food but they have to make you learn that no one can eat free forever. 

I kept thinking about this and ... frankly, if you are completely F2P player, it is really really really hard (like 10%) to complete last fusion, you will need to save at least 3 months. Here is the reason:

* The most tricky parts in all fusions are Champion Chase Tournament & Summon Event. 

- CCTour is easier, you could reach 2000 points by saving about 1000 green shards + looting champ in campaign + fragment fusem, etc.

- Summon Event is F2P-unfriendly event , you must pull shard to earn each single point. Last event required at least 2650 points, i.e. 5+ sacred shards or 25+ void shards or 130+ blue shards. I had to pull 4 sacred shards + some blue & green <- this says no to most F2P, unless you join in strong clans that kill UNM every day.