Wow difficult to choose from so many either below average footballers or footballers absolutely nowhere near value for money.
Koeman, Allardyce and Walsh were a poisonous mix, it's because of their lack of vision and thought that our wage bill is incredibly bloated and we have to cut back significantly on spend.
As for the players:
3 - Williams: Did ok in his first season but his second season was one of the worst seasons I've ever seen for any defender - and I used to laugh at Bramble and Boumsong at Newcastle! I honestly cannot believe he was captain for Swansea and Wales, did he show any real leadership at Everton?
2 - Bolasie: Of course it wasn't his fault he had a hefty pricetag, however it was Tweedledee Koeman and Tweedledum Walsh who thought spending nearly £30m on him would be wise and thinking he would take us to the next level. He wasn't particularly great even before his injury. At the age we bought him we were never going to be able to sell him on for a good fee even if he proved decent and for a player who was one of the most expensive players in our history at the time, 2 years later he is playing on loan in the next division down. What a mess of a transfer and now he's back here thinking he can compete with Richarlison, Bernard, Lookman, Walcott and Sigurdsson for a place in the team?
1 - Klaassen: The biggest disappointment for me given his potential, apart from maybe spells against the 4th best team in Slovakia he never really looked comfortable and when 4 managers of completely different football styles, visions and personalities all very early on decide that you have no real place in the team then alarm bells ring. Having grown up watching Everton during the stingy Moyes era, I still have to wonder if I'm dreaming that Everton are in a position where they can simply drop a £25m player out of the 16 man squad.
Other dishonourable mentions:
Schneiderlin - Did quite well in the first 6 months but really don't know how he could have declined so badly. Again a big money signing very close to being 30, he just seems to be the kind of player who would only do well if the rest of the team is playing well. Seems too much like a passenger at times and doubt his heart has been in it at times. However this season it sounds like there have been some personal issues as well, perhaps it is best he's been kept out the spotlight by Silva.
Tosun - We've paid quite a lot of money for a striker that hardly gets used, even the last manager who brought him in bizarrely had deep reservations about him early on. It's very difficult to see how Tosun fits into the team so I can't see a future for him. He will also suffer slightly from the fact that he was brought in pretty much to replace Romelu Lukaku but if anything he's been James Beattie's successor.
Sigurdsson - Overall he's actually done pretty well for us however if you are going to break significantly your transfer record for a player especially at the value of £45m, they should meet 2 criteria - 1)They should be of a sufficient quality to take the club up to the next level and be a player that the top 6 are envious of; 2) The manager who wants the player to come in so desperately should be able to build the team around this player's strengths so that they are able to get the most out of them. However 1) While he is a good player, I don't really think he is anywhere near a world class player; 2) We already had Rooney playing in his favoured position so Koeman practically stuck Sigurdsson out on the wing and in his first season this attacking player struggled quite often in a team that became famous for not registering many shots on goal.
Hopefully now that Brands is there and Moshiri has re-evaluated the way we do transfer business, whilst it has been a very expensive lesson for everyone involved at the club, we should on the whole make much better decisions going forward.