I am going to present a powerful system with White to fight against the main old line of the Scandinavian Defence.
Me!- riga1960 https://www.chess.com/game/live/52470031391
1. e4 d5
2. exd5 Qxd5
3. Nc3 Qa5
4. d4 Nf6
5. Bd2!?
This apparently humble move is much less played than 5. Nf3. As we shall see, however, White has good reasons not to occupy the f3 square with its knight. In some scenarios, White may like to play Qf3 and castle long quickly, and the knight g1 may be better placed in e2 than in f3.
5. ...c6
6. Bc4
Black has to keep an eye against d5 and Nd5. In the long run, the queen will have to be relocated somewhere else.
6. ...Bg4?!
This hyper-aggressive move is not justified here. White is happy to play f3 and start an expansion on the kingside. Better would have been 6...Bf5.
7. f3! Bf5
8. Ne2 e6
9. g4! Bg6
It is only move-9, but Black is already in a critical position.
10. h4 h5
White would continue the same way against 10...h6.
11. Nf4 Bg6
Black should not allow having its pawn structure completely spoiled if he can avoid it.
12. g5! Nfd7
13. g6
But he cannot avoid it...At the price of just one pawn, White obtains several weaknesses in Black's position (particularly the pawns e6 and g6).
13. ...Bxg6
14. Nxg6 fxg6
15. Qe2!
Simple and strong. The pawn cannot be defended.
15...Qc7
16. Qxe6+ Kd8
By the mean of natural moves, White has reached a winning position. Now it is a matter of technique. In general, when you are winning you better not hurry. If your opponent has a statically worse position such in this case (exposed king, pawn weaknesses, lack of development), it is often enough to complete the development and bring the last pieces to the attack.
17. 0-0-0 Qd6
White does not want to trade queens, which would alleviate Black's king sufference.
18. Bg5+ Kc7
19. Qe3 Qb4
White was threatening a dreadful pin with Bf4. After 19...Qb4, White has to think for real (maybe for the first time during the game). In general, when you are positionally winning, there is no reason to enter complications, which can only favour the side that is losing. A simple move like 20.Bb3 would have worked wonders here. However, I played...
20. Qe8
My justification was that Black cannot capture the bishop without getting mated with 20...Qxc4? 21. Bd8+ Kd6 22.Ne4+ Kd5 23.Qf7#
Instead, Black played
20. ...Na6
Black won't get immediately mated, but its position remains lost.
21. Qxa8 Qxc4
22. Qd8+ Kd6
23. Rhe1
Again simple chess. White activates the last piece threatening Bf4#. The game is already over, but Black played for a few more moves.
23. ...c5
24. Bf4+ Kc6
25. d5+
The queen is lost and checkmate follows soon.